axwell - TU Delft

AvionicsThe main contributor to innovation in aviation

Nuna5What went wrong?

Controlling the brainGraduation report

axwell

Edition 13.3Alumni edition

April 2010

M Magazine of the Electrotechnische Vereeniging

2 Maxwell 13.2 January 2010

HIER INVOEGEN:PAGINA2NEN.PDF

Maxwell 13.3 April 2010 3

From the BoardYou find in your possession this year’s alumni edition of Maxwell. This is an extra

thick edition of our quarterly magazine, which we are quite proud of. It represents an

important method for us to stay in contact with graduated electrical engineers. This

contact is important to us, as we aim to give people the opportunity to broaden their

view on their field of study and provide information about jobs and companies that

could be interesting to them. Henceforth, if you know an electrical engineer with an

interesting position, or if you would like to share your own experiences, please don’t

hesitate to contact us.

To follow, this quarter we made sure that aspiring electrical engineers got a chance

to open their minds to a wide variety of new ideas and projects. We went to CeBit in

Hannover, went on an excursion to Shell in Moerdijk, where we visited their chemi-

cal plant, and received a lunch lecture from Technolution. But of course, visiting

companies is not the only way to broaden your view on our profession. One big thing

we are working on at the moment is the organisation of the EESTEC exchange. The

European organisation EESTEC has the aim to bring electrical engineering students

from all over Europe together to give them the opportunity to experience foreign cul-

tures. In June there will be an exchange to Delft, which a committee of the ETV will

organise. To coordinate the activities of the EESTEC organization all members meet

once a year at a congress to speak about the plans for the organization for next year,

to elect a new EESTEC board and to sort out the financial affairs of the organization.

This year this congress took place in Athens where Delft was represented by two

The Board with the delicious cream pie

The Board visiting honoree member De Kroes

Jan and Frank in Athens

Board members of the ETV, Frank Teunisse and Jan Christiaanse. They had a great

week and gave a lot of useful input on the meetings.

That same week it was the ETV’s Dies. On the 23rd of March we had a huge home-

made pie in the faculty hall. It took two full days to make, but it was worth all the trouble. The pie was absolutely delicious.

Aside from all the activities the Board also visits the honoree members of the association. The ETV has 12 honoree members. These

people are usually visited once a year by the Board of the ETV. We have heard a lot of stories about their carreers and experiences,

what it was like to be a student and how they have been keeping themselves busy.

But most of the time you can find us in the Board room of the ETV. So if you like to meet some other students in a relaxed atmos-

phere, just drop along for a free cup of coffee.

On behalf of the inviting Board,

Imke Zimmerling, President

4 Maxwell 13.3 April 2010

ETV MAGAZINE “MAXWELL” Year 13 – edition 3 – April 2010 PRINTING Thieme Media Services, Delft NUMBER OF COPIES 5500 EDITORS Ben Allen, Joost van Driel, Benjamin Gardiner, Stephan Groot, Maarten Kastelein, Jeroen Ouweneel, Imke Zimmerling CONTACT Maxwell, p/a Electrotechnische Vereeniging, Mekelweg 4, 2628 CD Delft, phone: 015-2786189 or 015-2781989, fax: 015-27 81002, e-mail: [email protected], website: www.etv.tudelft.nl CHANGE OF ADDRESS Please send your changes to the address above, or use the website. Alumni can change their address via the Alumni Office website: www.alumni.tudelft.nl. ADVERTISEMENTS ASML (p.47), Farnell (p.48), Mastervolt (p.29), Navigon (p.35), NEN (p.2), Pinewood (p.35), Smit (p.15), Technolution (p.45), TNO (p.21) SUBSCRIPTIONS Non-members can receive the Maxwell four times a year, against a contribution of €10,- per year. For more information, please contact the Maxwell Committee.

Editorial

Although every single edition of the Maxwell on its own is special, once a year the entire Maxwell Committe prepares itself for her yearly magnum opus. By reading this, you’ve reached the fourth page of the Alumni edition of already the thir-teenth year of the Maxwell. For the committee the alumni edition always provides an extra chal-lenge, as it contains more pages to fill with inter-esting content than a regular edition.

What to expect of this Maxwell? Besides the usu-al sections like the From the Board, the news-flash and an overview of the recent activities of the Electrotechnische Vereeniging, the Maxwell Committee tried to provide you with an article about every branch of Electrical Engineering. From the Telecommunications angle an article about the communication network of the Dutch emergency services C2000 is presented. Marijn van Dongen provides a report about his master thesis work, by which also Microelectronics is represented. An insight in the development in the powering of trams is given by Professor van der Sluis from Power Engineering. Last, some Computer Engineering topics are touched upon by two different companies. The Austrian com-pany TTTech explains its adaptation of the exisit-ing Ethernet. The Dutch Technolution explained how difficult it is to use the GPU for other pro-cessing tasks.

To conclude, I expect that you will have some pleasant hours reading this edition of the Max-well. For any remarks, complaints or other co-ments, please feel free to contact the Maxwell Committee.

Stephan Groot

Contents

Controlling the brain

Avionics

12

22


From the board 3 Newsfl ash 6 Educational announcements 8 FSR 8 Activities of the ETV 9 Cooking with: Rob Remis 28 TTEthernet 30

Joost may know it 34 Circuit 38 Per elektrische scooter naar Kopenhagen 40 Gadgets 42 Technolution: GPU 43 Column: Prof. Ligthart 46

C2000: Life-saving communication?

Innovatie intrammetjesland

NuNa 5:What went wrong?

16

26

36


Newsfl ash

Skinput: a touchscreen on your armPaul Marks, New Scientist

Finding the keypad on your cellphone or music player a bit

cramped? Maybe your forearm could be more accommodating.

It could become part of a skin-based interface that effectively

turns your body into a touchscreen. Called Skinput, the sys-

tem is a marriage of two technologies: the ability to detect the

ultralow-frequency sound produced by tapping the skin with a

fi nger, and the microchip-sized “pico” projectors now found in

some cellphones.

The system beams a keyboard or menu onto the user’s forearm

and hand from a projector housed in an armband. An acous-

tic detector, also in the armband, then cal-

culates which part of the display you want

to activate. But how does the system know

which icon, button or fi nger you tapped?

Chris Harrison at Carnegie Mellon Univer-

sity in Pittsburgh, Pennsylvania, working

with Dan Morris and Desney Tan at Micro-

soft’s research lab in Redmond, Washington,

exploit the way our skin, musculature and

skeleton combine to make distinctive sounds when we tap on

different parts of the arm, palm, fi ngers and thumb.

They have identifi ed various locations on the forearm and hand

that produce characteristic acoustic patterns when tapped. The

acoustic detector in the armband contains fi ve piezoelectric

cantilevers, each weighted to respond to certain bands of sound

frequencies. Different combinations of the sensors are activated

to differing degrees depending on where the arm is tapped.

Twenty volunteers tested the system and most found it easy

to navigate through icons on the forearm and tap fi ngers to

actuate commands. Skinput works very well for a series of ges-

tures, even when the body is in motion, the

researchers say, with subjects able to scroll

through menus whether they moved up and

down or fl icked across their arm. The sys-

tem could use wireless technology like Blue-

tooth to transmit commands to many types

of devices. The researchers will present their

work in April at the ACM Computer-Human

Interaction meeting in Atlanta, Georgia.

Figure 1: The Skinput-system projecting

buttons on an arm.

MIT makes display with fl ying pixelsImagine that pixels could fl y out of your computer screen and

create an immersive, luminous cloud capable of displaying

digital information in three-dimensional space. This is the

vision beyond Flyfi re, a new project put together by research-

ers at MIT’s SENSEable City Lab and Aerospace Robotics and

Embedded Systems Laboratory (ARES Lab). Flyfi re uses a large

number of remotely controlled, self-organizing “micro helicop-

ters”. Each helicopter contains small LEDs and acts as a smart

pixel. Through digitally controlled movements, the helicopters

perform elaborate and synchronized choreographies, generating

a unique free-form display in three-dimensional space.

Using the self-stabilizing and precise controlling technology de-

veloped by the ARES Lab, the motion of the pixels is adaptable

in real time. The Flyfi re canvas can transform itself from one

shape to another or bring a two-dimensional photographic im-

age into an articulated shape (background image). “Today we

are able to simultaneously control a handful of micro helicop-

ters, but with Flyfi re we are aiming to scale up and reach very

large numbers,” said Emilio Frazzoli, head of the ARES Lab.

“Flyfi re opens up exciting possibilities: as on a conventional

screen, pixels can change color, but now they can also move,

creating a transient trace of light in three-dimensional space,”

said team member Carnaven Chiu. “Unlike traditional displays

that can only be seen from the front, Flyfi re becomes a three

dimensional immersive display that can be experienced from

all directions.” Flyfi re is conceived as a public space installa-

tion, in which the pixels recharge every few minutes and then

perform in space. “In general, there are two ways to increase

the resolution of a display,” said Carlo Ratti, director of the

SENSEable City Lab.

“One is to use smaller pixels.The other one is to look at it from

farther away. Flyfi re adopts the second approach to create a

unique visual experience in large public spaces.” Flyfi re is made

possible by recent advances in battery technology and wireless

control. It aims to be a step towards ‘smart dust’, the idea that

computing is becoming increasingly smaller, addressable, per-

vasive - and persuasive. The Flyfi re project was developed by

E. Roon Kang, Carnaven Chiu, Caitlin Zacharias, Shaocong

Zhou, Assaf Biderman and Carlo Ratti of SENSEable City

Lab in collaboration with Erich Mueller and Emilio Frazzoli of

ARES Lab.

Source: http://senseable.mit.edu/flyfire


Record communication speeds over ceiling lightsResearchers at Fraunhofer Heinrich Hertz Institute in Berlin

together with their Siemens colleagues have scored a peak data

rate of 500 megabits per second (Mbit/s) using off-the-shelf

LED lights. The new benchmark breaks the previous record

they held of 200 Mbit/s. Data transport over visible light is a

means of transmission that is license-free, and tap-proof and

that opens the way for a range of novel applications in the

home, industry and transport.

Researchers at Siemens Corporate Technology in Munich and

the Heinrich Hertz Institute set the new

free space data transmission record for a

distance of up to 5 meters using a white

light emitting diode from the Siemens

subsidiary Osram. Data were directly

modulated from the supply current onto

the quantity of light emitted by the LED.

The Ostar LED used is one of the bright-

est now on the market and can be modu-

lated so rapidly that a highspeed

data transmission rate of 500 Mbit/s

can be achieved while the human

eye detects no change in the level

of brightness. The receiver is a photodetector that transforms

light signals into electrical impulses.

Visible Light Communication (VLC) is a medium that holds

out the promise of a wide range of applications. In the home

it can be a valuable extension to established WLAN technolo-

gies as in many buildings wireless networks are increasingly

impeded by clogging of the three independent WLAN frequen-

cy bands which leads to collisions between data packets. As a

license-free and previously unexploited medium, visible light

offers a viable alternative. A further key advantage is that VLC

also offers tap-proof secure lines as only the receiver located

directly in the light cone can receive the transmitted data, thus

precluding any “eavesdropping” on the light beam. In factories

and medical technology there is a need for data transmission in

places where wireless cannot be deployed or only to a limited

extent. Yet another area of application is in

the transport domain where LED traf-

fic lights and railway signals can relay

information to cars and trains.

The researchers also demonstrated

that a network of up to five LEDs is

capable of achieving data transmis-

sion speeds of up to 100 Mbit/s over a

longer distance. This is a critical point for prac-

tical applications as, for instance, data from ceiling lights

can then be sent to a receiver on a desktop no matter where

the desk is positioned in the room. Since 2007 the Institute of

Electrical and Electronics Engineers (IEEE) has been working on

standardization of the technology in a procedure scheduled for

completion by late 2010.

Source: http://www.hhi.fraunhofer.de.

Figure 2: The principle of

LED-light communication.

Babbage nanomachine promises low-energy com-putingNot only did Charles Babbage lay the foundations for the com-

puter revolution, his designs for mechanical computers also

provide a blueprint for energy efficiency. So say Raj Mohanty

of Boston University and his colleagues, who have created a

nanoscale mechanical logic gate that could form the basis of

tiny mechanical computers.

The gate consists of a strip of silicon 300 nanometres wide sit-

ting between two chunks of silicon. Applying a voltage between

one chunk and the strip causes the strip to vibrate, like the reed

in a clarinet. With the right voltage, the strip will enter a so-

called hysteretic regime - where it will vibrate with one of two

amplitudes.

“The two amplitude states are separated by a potential barrier,”

says Mohanty. By using a pair of electrical pulses that work

with the resonating strip to provide that kick in potential, the

team were able to flip the vibration from one amplitude to the

other. If just one of the pulses - or neither of them - resonates

with the strip then it remains in its existing vibrational state.

In other words, says Mohanty, the device acts as an AND logic

gate (Nano Letters, DOI: 10.1021/nl9034175).

While the gate is not as fast as its traditional equivalent, it loses

far less energy per operation, Mohanty claims. “When you have

millions of devices on a chip, energy loss adds up,” he says.

Trading speed for energy might be beneficial in some situations.

Source: http://www.newscientist.com/

Figure 3: The new chip, with inputs and output.


Educational Announcements

MIGRATION TO OSIRIS

Osiris is now almost fully functional, and the migration of the

ISPs is also almost fi nished. Starting next quarter, subscrip-

tions for exams have to be done in Osiris. Furthermore, from

now on there will be a single deadline for subscribing for all

exams. For the fourth quarter, this deadline will be June 6th.

NEW TIMETABLE SOFTWARE IN BLACKBOARD

You can now create, store and view your personal timetable in

blackboard. A group of enthusiastic Computer Science students

were unhappy with the timetable site that was introduced last sum-

mer, and built a new, improved one. You can now create your time-

table based on the courses you are enrolled to, by study program

or individual. The software can export to iCal, CSV and PDF and

can be found in Blackboard.

STRESS ON THE THIRD FLOOR OF EWI

On the third fl oor people are working harder than ever. The

Bachelor and Master Electrical Engineering and the Master

Computer Engineering are about to be inspected. As such, our

whole education system has to be evaluated. Furthermore, a

new Bachelor program is in the pipeline. The plan is that up-

coming freshmen will start with a study program that is much

more project orientated.

RESEARCH INFORMATION FOR (BACHELOR) STUDENTS

Most Bachelor students have little idea of what goes on in the EWI

tower. That’s why the ETV, in cooperation with EWI Marketing,

is organising an event in May were every research group can talk

about the exciting research they are currently working on. Students

will hear more about this event as details are confi rmed.

De Facultaire StudentenraadWij als facultaire studentenraad, of kort FSR, zijn alweer een tijdje bezig en houden de faculteit goed in de gaten. We hebben in het begin

van het collegejaar een 10-puntenplan gemaakt met de 10-punten waar wij dit jaar extra aandacht aan geven. Dit doen wij vooral in onze

maandelijkse overlegvergadering met de decaan, maar ook in verschillende werkgroepen in de faculteit, waar onze mening gevraagd is. Een

paar van deze punten hebben wij hier even kort toegelicht.

INVOERING VAN DE HARDE KNIP EN HET BINDEND STU-

DIEADVIES.

Eerstejaars krijgen voor het eerst te maken met het bindend

studie advies, dat betekent dat ze tijdens hun eerste jaar mini-

maal 30 ECTS moeten halen en anders helaas niet verder mo-

gen met hun studie. Verder krijgt iedereen uit 2006 en later na

dit jaar te maken met de harde knip: eerst alle punten uit je ba-

chelor halen voor je verder mag met je master. Zowel rondom

het BSA als de harde knip zijn harde afspraken gemaakt door

de studentenraad en wij zullen er op toezien dat deze binnen

onze faculteit nageleefd worden.

UITSTRALING VAN DE FACULTEIT

We zijn dit jaar bezig de uitstraling van onze faculteit te verbeteren.

Zowel het hoofdgebouw als gebouw 35 stralen niet uit dat het EWI

gebouwen zijn, terwijl dat wel zou moeten. Heb jij werkbare ideeën

over de invulling van dit idee, laat dat dan weten!

DIPLOMAUITREIKINGEN

De ceremonie zoals deze op dit moment een aantal keer per jaar

plaatsvind wordt door velen als saai ervaren. We zoeken naar een

oplossing om de uitreikingen leuker te maken terwijl de studenten

die hun diploma ophalen toch de verdiende aandacht krijgen. Ook

ideeen hierover horen we graag van jullie.

Deze punten krijgen bijzondere aandacht van ons, maar ook alle andere problemen pakken wij natuurlijk aan. Dus heb jij een idee over een

van de bovengenoemde punten of kom je zelf andere problemen tegen? Laat dat dan weten via [email protected] of spreek een van ons

aan op de faculteit. Er is altijd wel iemand te vinden bij de ETV of CH, we zijn te herkennen aan de foto’s op de posters die door de hele

faculteit hangen. Vergeet ook niet je stem te laten horen bij de volgende verkiezingen van de FSR op 26 en 27 mei!

The faculty of Electrical Engineering, Mathematics and Computer Science is con-

stantly undergoing evaluation and change. Here are the most important goings-on

in our faculty at this moment.

Author: Frank Teunisse, Commissioner of Education


Activities of the

Electrotechnische Vereeniging

Excursie CeBIT Auteur: Patrick Fuchs

Daar stond ik dan ‘s ochtends (4 uur!) met mijn

slaapogen de rest van de groep te zoeken. Toen de

bus eindelijk kwam kon ik mijn ogen niet gelo-

ven (misschien ook omdat ik m’n contactlenzen

niet in had). Dit was de meest luxe bus die ik

ooit had gezien. Misschien waren het de zacht

leren stoelen, of de vroege vertrektijd, en mis-

schien een combinatie van beiden, maar ik lag

wel heel snel te slapen achterin de bus.

Enkele uren later (weer wat opgefrist na een re-

delijke nachtrust) kwamen we aan op het “mes-

segelaende” waar CeBIT plaatsvindt. Even la-

ter stonden we met z’n allen in de eerste zaal.

Als eerste natuurlijk langs bij Alcatel-Lucent,

die onze kaartjes voor de entree van de CeBIT

beurs betaald hadden. Daarna viel de groep re-

delijk snel uit elkaar en ging iedereen naar de stands of hallen

waar ze het meest interesse in hadden. Omdat het beursterrein

zo groot was (te vergelijken met het centrale deel van de TU

Delft-campus in grootte), had ik sommige mensen de hele dag

niet gezien. Aangezien dit de eerste keer was dat ik überhaupt

op een ICT-beurs was (afgezien van de Games Convention

Leipzig, waar het zwaartepunt toch ergens anders ligt) was ik

maar wat gaan lopen, op zoek naar leuke gadgets en goodies.

Dan waren er ook nog de 3D-schermen en -technieken die al-

lemaal naast elkaar geshowd werden. Dit trok natuurlijk de

aandacht van veel mensen, maar weerhield ons er echter niet

van ook zelf deze brilletjes en beeldschermen te ge-

bruiken en te bekijken. Erover horen is een ding,

maar zelf de verschillen vooral waarnemen geeft

natuurlijk een heel ander (3D-) beeld. Nadat uwe

reporter zelf geïnterviewd was door een Russische

tv-zender (over een 3D-bril die ik aan het “testen”

was, vond ik het welletjes en gingen we door naar de

rest van de hallen.

Jammer genoeg ging de terugreis niet helemaal zon-

der problemen. We waren namelijk iemand kwijt-

geraakt op de CeBIT (waarschijnlijk onderweg naar

Hannover voor het avondeten, voor de details moet

je maar het Bestuur vragen) waardoor we meer dan

een uur vertraging opliepen. Achteraf was iedereen

gelukkig naar Delft gekomen en was het een zeer

geslaagde excursie.

Zelfs binnen de grote mensenmassa waren de ETV’ers vanouds goed te onderscheiden.

De nieuwste gadgets van Asus.


De deelnemers van de Shell-excursie.

Excursie Shell Auteur: Felix Fikke

Op het moment dat voor de meeste studenten het eerste col-

lege begon, verzamelde op 16 maart een groep enthousiaste

ETV’ers zich op het station van Delft. De reis leidde naar

Moerdijk, alwaar we, samen met een delegatie uit Eindhoven,

een bezoek brachten aan Shell. De dag was georganiseerd en

werd begeleid door Alexander Bosman, een jonge elektro’er die

sinds 4 jaar voor Shell werkt. Zoals te verwachten van iemand

met deze achtergrond was de dag perfect georganiseerd.

We begonnen met een kleine rondvraag om vast te stellen wat

men over het werken bij Shell zou willen weten. Daarna vertel-

de Alexander over de diversiteit aan carrièremogelijkheden die

een multinational als Shell bood. Gevolgd door een presentatie

van Joke Driessen met een algemeen praatje over Shell Moer-

dijk. Deze fabriek is een van de grootste kraakfaciliteiten in

Europa. Hier wordt per jaar zo’n 4,5 miljoen ton ruwe aardolie

verwerkt tot Nafta, aardgas en andere producten.

Na de presentatie van Joke was het woord aan Wim de Wilt, de

‘global manager Electrical Engineering’ voor Shell. Hij vertelde

boeiend over zijn langdurige carrière bij Shell en beantwoorde

een hoop van de in het begin gestelde vragen. Hierna was er ge-

legenheid om tijdens een kleine lunch met één van de diverse

werknemers gesprekjes te voeren en informatie op te doen.

Na de lunch werden we voorzien van beschermende kleding,

waarna we een rondleiding door de fabriek kregen. Ons groepje

werd begeleid door een oud elektro’er uit Delft. Hij leidde ons

langs de kraakovens, transformatoren en andere grote machi-

nes. Erg interessant was natuurlijk de controlekamer waar de

stroomvoorziening geregeld word.

Als afsluiting kregen we nog een aantal zeer waardevolle tips

over het solliciteren en stage lopen bij Shell, waarna we ver-

moeid doch voldaan terugkeerden naar Delft.

Lunch lecture Technolution Author: Lucas van Dijk

On the 9th of March, Dr.ir. Paul van Haren visited our faculty

to tell something about Technolution. It was defi nitely a good

and informative lecture, which showed a bit about their design-

process for a system they’re developing for Philips. He started

off telling in what fi elds Technolution is active. Examples are

traffi c engineering (NS, ProRail, Rijkswaterstaat), High-Tech

(Philips, ASML, OCE and Agfa), and some other fi elds like

telecom and power engineering (KPN, Motorola, Eneco). It’s

nice to know that Technolution provides solutions to certain

problems with existing technology, they don’t do any research.

In Holland, there’s only one offi ce, and it’s located in Gouda.

If I may believe Dr.ir. Paul van Haren, there’s a nice atmos-

phere at their company, discussing a lot of new technologies

colleagues have discovered. People who fi nished an electrical

engineering, computer science, mathematics or physics study

are always required at Technolution as these kinds of people

often have a lot of knowlegde in one or more of the following

fi elds: electronics, embedded systems, programmeable logic or

information systems. In their experience, people from electri-

cal engineering can be used in all four fi elds, but who expected

anything else?

After this part, that was mainly about Technolution, he contin-

ued describing the design process of a machine which can sort

of look inside your body without making any cut. The screen

where the inside of the body will be displayed, is huge. Besides

only the body view it contains six ‘subscreens’ which all dis-

play data like patient information, machine position, and all

you can think of. The resolution of this screen was around

4000x3000 if I’m right, so a good graphicscard is required. It

also allows to add external devices to the screen through a DVI

connector. They designed their own DVI grabber which can be

put in a PCI-E 2.0 slot, and it actually does a lot more than

only grabbing the DVI signal: it also compresses and crops the

view a bit, because there wouldn’t be enough bandwidth avail-

able on a PCI-E 2.0 slot to grab 4 external devices at the same

time.

There was more on the lecture, but I hope this has given you

a good idea about the lecture. They defi nitely got my interest,

because it sounds like a great company which works on a lot of

different projects, in all sorts of fi elds.


Eestec LC Delft Author: Jean-paul Schouwstra

The ETV is a member of the international organization EESTEC, where it is known as EESTEC LC (Local Committee)

Delft. The main objective of EESTEC is to improve contacts between electrical engineering students from all over Europe.

This is achieved by organizing exchanges, an annual conference, workshops and other great activities. The principle of

EESTEC is simple: if you arrange your own trip to your destination location, your accommodation, food and program will

be arranged for you. All of the 40 LC’s organize an exchange at least once every two year. Activities that participating stu-

dents can expect are cultural activities, workshops, lectures and most importantly multicultural integration between the

students from all the different countries. Do you like this principle and want to stay up to date once a month on upcoming

activities and exchanges? Contact [email protected] and subscribe for the Eestec-newsletter!

For this year an enthusiast committee of the ETV started preparing an exchange to Delft. The theme of this exchange is

“Size Does Matter”. To prove this we have a very large committee, especially compared to other years. This committee will

ensure that the week of June the 7th will be an incredible, unforgettable week for the international guests as well as for the

Delft students participating.

Wouldn’t you like to be brought in contact with a nice foreign electrical engineering student? Well this is your chance. For

our exchange to Delft we are still looking for some hosts to provide sleeping places for international students for one week.

So if YOU still have some free square meters, please let us know by e-mailing [email protected]! In return you’ll be

able to go to some GREAT parties and get the chance to “keer” an exchange student.

An impression of the last EESTEC-exchange in Delft.


Since July 1, 2004 C2000 replaced the an-

alog communication networks of Dutch

emergency services. Nowadays the police

forces, fire departments, ambulances and

the Koninklijke Marechausee (a force pro-

viding military police and civil police du-

ties) all use the C2000 system for their

communication. Recently, this system

caused quite some unrest in the Nether-

lands, due to some possible failures of the

system during some major events. In this

article the concerns that are associated

with C2000, will be pointed out.

Before we look at the issues that arose

with C2000, we first address the reasons

for the transfer to C2000. After that a

brief technical analysis of the C2000 sys-

tem will be given. Finally, the problems

that arose in using C2000 will be pointed

out.

From analog to digitalIn the mid nineties there were several de-

velopments, which caused an understand-

ing among the Dutch emergency services

that it was necessary to replace the old

analog communications networks. Be-

sides the general tendency towards the

digital era, one of the main developments

was the insight that the analog system

was not providing enough capacity and

lacked in security. Besides that, the ana-

log system did not provide the possibility

for the different emergency services, like

the police, fire squad and ambulances, to

communicate with each other. Both the

evaluation from the fire at Volendam dur-

ing the turn of the year 2000 to 2001 and

the evaluation of the fireworks explosion

“We need immediate assistance at the Mekelweg 4 in Delft. Over”. “Unit Echo Tango Victor is on

route. Over and out”. Seems like a random example of a possible communication message between a

mobile unit and the radio control room of one of the emergency services. It holds in general that com-

munication is of vital importance in the operation of emergency services. Therefore it is easily under-

stood that the communication network of the emergency services in the Netherlands, C2000, recently

received a lot of attention due to some possible failures of the system.

C2000Life saving communication?

Author: Stephan Groot


in Enschede, confirmed these issues some

years later.

In September 2004 the C2000 was intro-

duced. It took three years before the last

police squad, the one of the region Am-

sterdam-Amstelland, shut their analog

network down and switched to C2000.

This completed the nationwide migra-

tion towards the digital C2000. C2000

belongs to the class of Private Mobile Ra-

dio (PMR) systems, which have different

requirements than the public communi-

cation networks. The specific demands of

users of PMR systems will be addressed

later. These demands cannot be satis-

fied by conventional system like GSM,

GSM-R and DECT. Therefore a standard,

especially suitable for PMR systems, like

C2000, is developed.

TETRAThe C2000 communication network

makes use of the standard TETRA,

which is an abbreviation for TErrestrial

Trunked RAdio. Trunking is a word bor-

rowed from the telephone system to de-

scribe a system, in which a large number

of users share a much smaller number of

communication paths. Traditionally, this

was related to a wire (the trunk) that was

assigned to a telephone user upon mak-

ing a call. In the case of terrestrial radio

the scarce resource is bandwidth. If we

relate this for example to the police in a

certain region, where there are at a given

time quite a number of police officers on

duty, who all need to stay in contact with

a dispatcher. If each officer would use an

exclusive channel, the available frequen-

cy band would soon run out of possible

channels. Moreover, this is not a very ef-

ficient way to assign radio channels, since

each channel would be idle most of the

time.

In a trunked radio system the total num-

bers of users are divided into groups. Im-

agine waiting with a group of friends for a

table at a crowded restaurant. You go up

to the hostess and give her your name,

and she puts it on a list with a bunch of

other names. If all the tables already have

people at them, you wait. When a table is

ready the hostess announces your name

over the speaker and you and your friends

follow her to the table she selected for you

(probably the first one that became avail-

able). This principle is also applicable

to the kind of trunking used in TETRA.

When a user of one group wants to talk to

a user of another group, he has to request

a channel assignment from a controller

first. The controller will check if there is a

channel free. If all the channels are occu-

pied, the controller makes you wait until

a channel is free, and then publicly an-

nounces your talk group and the assigned

channel. User A and the intended receiv-

ing users then switch to that channel and

can communicate with each other.

Trunking can be applied to both a part

of the conversation or to the entire con-

versation. The first is implemented in

TETRA. In this case a conversation that

takes place over several transmissions

may actually occur on several different ra-

dio channels because the controller may

assign a new channel every time someone

presses their push-to-talk button. This

is the most efficient way to share radio

channels, since other people can use the

channel during pauses in the conversa-

tion, but it is also what makes it more

difficult for a normal scanner to listen in.

At this point, one can wonder why use

a complete different standard instead of

proven technology like GSM. The rea-

son for this is the specific requirements

that communication networks for emer-

gency services demand. The traditional

techniques, like GSM, have certain is-

sues, discussed here, which are solved in

C2000.

GSM limits the amount of subscribers

in a group to 1024 and the amount of

dispatchers to 5. In TETRA no restric-

tions on group size are defined, but a

group can deal with at most 30 dispatch-

ers. Especially the relative small number

of possible dispatchers in GSM is a limi-

tation, since one of the objectives of the

network is to enable different emergen-

cy services to communicate with each

other. This requires many dispatchers.

A very effective way of informing mem-

bers of a group in case of an emergency

is trough sending a short data message

to each member of the group. This func-

tion is defined in TETRA, but is not

available in GSM. Of course it is pos-

sible to send a SMS in GSM to each

member of the group individually. How-

ever, this is significantly slower than the

service TETRA provides. Besides that,

since SMS data files run over the signal-

ing channel of GSM, this will put a sig-

nificant additional load on the signaling

channel, when used extensively.

Another rather important difference

origins in the way how both handle

call priorities. Call priorities are speci-

fied for both TETRA and GSM. How-

ever, TETRA is more flexible in this

case, because it can provide different

priorities to a user or group. Further-

more, in TETRA more priority classes

are specified. Another rather impor-

tant feature of TETRA that is not in-

corporated in GSM is the speech item

priority. In for example emergency

situations it can be important that

a group leader can get a speech item

and force the other subscribers in the

group to listen. This feature can be

important to achieve organized com-

munications, which can be critical in

an emergency situation.

When designing a communication

network for the emergency service

the call set-up time is of huge impor-

tance. In C2000 it is required that a

call can be set-up within 0.5 seconds.

With some efforts the call set-up time

in GSM can only be reduced to one

second.


The security of the network is of ex-

treme importance for the intended

users of C2000. The security should

ensure that someone not belonging to

a certain group is unable to listen to

the communication, but also is un-

able to disturb the communication.

In TETRA three types of security

measures are implemented. First, au-

thentication ensures that only users

with a valid key can use the network.

Moreover, the call information, the

control information and the identity

of the users is encrypted, by a so-

called Air Interface Encryption (AIE)

protocol. This ensures that a user can

be tracked by following the signal-

ing messages on the control channel.

Last, encryption between the end-

points of communication is provided.

End-to-end encryption (e2ee) prevents

eavesdropping by encrypting the in-

formation on the traffic channel. The

difference with AIE is that the infor-

mation on the control channel isn’t

encrypted.

IssuesIn 2009 there were several incidents,

which caused some distrust in the C2000

system. In February a passenger flight of

Turkish Airlines crashed near Schiphol

Airport. During the rescue the system had

signs of overloading. For example many

people couldn’t get a proper connection

using their radio. Afterwards, the Inspec-

tion for Public Order and Safety conclud-

ed that the available 11 groups were too

little for the vast number of emergency

services on site. Another, and maybe one

of the most well-known, example of the

disfunctioning of C2000 is during the

riots on the beach of Hoek van Holland.

When the situation escalated, again, the

system showed signs of overloading. The

police men on site couldn’t communicate

with each other for some time.

As a result of these incident, the Depart-

ment of Interior Affairs has investigated

the operation of C2000. One of the out-

comes of this investigation is that there

are some locations in the Netherlands,

where the coverage of C2000 is not suf-

ficient. At these locations the link tends

to switch between two different base sta-

tions, hence drastically deteriorating the

connection. These locations are collected

in a so-called DIPP list (Dekkings Is-

sue Prioritering Procedure, in short this

means a collection of the important lo-

cations, where coverage problems arise).

This DIPP list also includes Pernis, where

the Dutch petrochemical industry is con-

centrated, Borssele, the location of a nu-

clear power plant and Vught, the location

of an extra secure prison. Recently was

announced the coverage of 60 high-risk

locations like these will be optimized

within two years.

Although some of the technical short-

comings of C2000 are recognized, the

influence of the user on the proper func-

tioning of C2000 also has to be taken

into account. For example when evalu-

ating the problems that arose during the

plane crash in February, it was concluded

emergency people were using their radio

for non-essential communication too. If

the radio was only used for the important

messages, the overloading of the network

could have been prevented. The failures

of the system, during the riots at Hoek

van Holland, but also during the attack

on Queen’s Day 2009 were ascribed to

the fact that there were too many us-

ers in the same group. The director of

the region Rotterdam-Rijnmond, Don

Berghuis, who was appointed for the re-

search, states that many emergency serv-

ice people all use the same group. There-

fore the system seems overloaded. In fact

this isn’t the case, but because there are

many users in one group, individual users

need to wait longer before they can speak.

When in critical situations people tend to

speak at the same time, this gives prob-

lems. Berghuis also added that this isn’t

a specific telecommunications problem.

If ten people are talking to each other in

person, communication also won’t work

if they talk at the same time. To solve this

problem, the users of C2000 are trained

again to work properly with the system.

ConclusionMore than a decade ago the Dutch emer-

gency services switched from an analog

communication network to a digital one:

C2000. Theoretically, this new commu-

nication network provides the emergency

services with state-of-the-art commu-

nication, providing in all their specific

demands. However, when using C2000

some issues arose. Especially during ma-

jor incidents, the system showed signs of

overloading. Investigations showed that

there exist both technical as user related

reasons for these issues. To overcome

the technical problem of too little base

stations at critical locations, the coming

years these base stations will be installed.

The users of C2000 are once again

trained, in order for them to work prop-

erly with the system. Maybe, these two

actions will finally enable the emergency

services to use their life saving communi-

cation system!

References:[1] Terrestrial Trunked Radio – TETRA, P.

Stavroulakis, Springer, 2007.

[2] Eindrapportage expertgroep C2000 –

Ministerie van Binnenlandse Zaken en

Koninkrijksrelaties, definitieve versie, 22

december 2009.

Maxwell 13.2 January 2010 15

HIER INVOEGEN:PAGINA15SMIT.PDF


The list of brain diseases is very long: Alzheimer's disease, Par-

kinson's disease, Tinnitus and mental disorders (e.g. clinical

depression or schizophrenia) are just a few of the well known

examples. All these diseases have major impact on the quality

of life of the patients. Existing treatments have only limited

effectiveness.

During my Master thesis I have looked into the design of a neu-

ral stimulator: a device which is able to directly infl uence the

functionality of the brain using electrical stimulation. It turned

Controlling the brainHow electrical stimulation can be used as an

effective treatment for many brain disorders.

out this leads to a very exciting research

fi eld with many challenges which need to be

solved; both in the medical as well as in the

electrical domain.

In this article an introduction will be given

in the fi eld of neural stimulation. The focus

will be on how the brain works from an elec-

trical point of view and how it is possible to

infl uence this functionality using stimula-

tion. Also an overview is given for the most

important innovative features our design is

providing compared to existing stimulators.

Why is brain stimulation effective?Throughout history medicine has been going

through an extensive development. Prehis-

toric medicine consisted of a combination of

very basic drugs (extracted from plants and

herbs) and treatments consisting of ceremo-

nies carried out by shamans using supernat-

ural powers and objects (charms, spells, am-

ulets, etc). During the course of history more

and more knowledge was gained about the

use of drugs for treating diseases. From the

19th century on medicine has gone through

a revolution thanks to advances in for exam-

Figure 1: Photo’s of the surgical procedure of implanting the electrodes for neural stimulation in the brain. In the right picture the electrode lead is inserted

in the brain (pictures courtesy of dr. D. de Ridder)

Our brain is the center of our nervous system. Literally everything we do,

from eating an apple to solving a Schrödinger equation, is controlled by

it. Usually we don’t give much thought to the fact our brain is so utterly

important, but imagine something starts to go drastically wrong inside the

brain. Not being able to solve a Schrödinger equation might not be a big

problem for the majority of people, but eating an apple is.

ple chemistry and today drugs form an utterly important ingre-

dient of medical treatments.

However it is more and more realized that drugs alone can-

not cure all diseases effi ciently enough. Most drugs suffer from

unwanted side effects and the spatial selectivity of drugs is usu-

ally low: it will have effects on the whole body, while usually a

disease is limited to only certain parts. Another form of treat-

ment consists of electromagnetic stimulation of the body. Cells

use electromagnetic signals to operate. These signals can be af-

Author: Marijn van Dongen


fected by artificially generated electromagnetic signals in order

to establish a desired effect.

Probably the most well known form of stimulation is the pace-

maker: a stimulator for the heart muscle. This particular tech-

nique has gone through an extensive development as well. As

early as 1820 Richard Reece described in his 'Medical Guide' a

method for stimulating the heart. A metal rod was inserted in

the esophagus and connected to a voltaic

cell, while another rod was pushed to

the chest by the physician. In this

way a 'manual' pacemaker was

comprised as depicted in Figure

2. Nowadays pacemakers are

very sophisticated implanta-

ble stimulators: they record

heart activity and based

on this activity the de-

vice can decide when

and how the heart

needs to be stimu-

lated.

The brain essentially

works in a similar man-

ner as the heart muscle:

neural cells communicate

by 'activating' each other

using electrical impulses.

This means that the activity of the brain can be affected by

means of electrical stimulation as well. As shown in the in-

troduction, many diseases find their origin in abnormal brain

functionality. It is therefore in principle possible to eliminate

this unwanted activity by using brain stimulation. This can be

done by implanting electrodes connected to a stimulator, which

can deliver stimulation pulses to the tissue.

In this way the functionality of the brain is directly influenced.

This results in a much more selective treatment. Side effects

are expected to be much smaller, thereby increasing the effec-

tiveness.

The development of neural stimulators is still in a relatively

early stage: in some way current stimulators are comparable

to the first pacemaker from 1820. Most stimulators have lim-

ited implantability as depicted in Figure 3. Furthermore they do

not incorporate any feedback: they simply stimulate the neural

tissue using a fixed stimulation pattern, without recording the

activity in order to adjust the stimulation if required.

How does neural stimulation work?Before we can start with the

design of a neural stimula-

tor, first a closer look is tak-

en at the physical principles

underlying electrical stimu-

lation. It is required to know

what exactly happens in the

tissue when electrical energy

is transferred to an electrode

implanted in the brain.

The brain consists of tens

of billions neural cells called

neurons. A neuron has a cell

body (soma) with a nucleus,

as depicted in Figure 4. The

inputs of the cell are called

dendrites and its output is called an axon. Input voltage pulses

coming from the dendrites (sometimes thousands of dendrites

are connected to a single neuron) are processed in the nucleus

and this can result in an output pulse in the axon. These pulses

form the fundamental mechanism for all actions in the central

nervous system.

The voltage pulses are transferred over the cell membrane,

which encloses the neurons and axons. Within this membrane

there are ion channels through which different types of ions

(mainly potassium, sodium and chloride) can flow. Due to a

concentration gradient of the ions between the inside and out-

side of the membrane, there is a continuous ion flow through

this membrane.

The flow of ions is determined by the conductance of the

channels, which turns out to be dependent on the membrane

voltage. This will eventually lead to a dynamic equilibrium in

which ions will flow with a constant rate, yielding a resting

potential of the membrane.

Changing the membrane voltage, will change the ion flow ac-

cordingly. When the membrane voltage is raised above a par-

ticular threshold, the membrane is 'activated' and a process is

triggered, which will result in a voltage pulse over the mem-

brane. This pulse, often referred to as an action potential, will

propagate over the axon towards other cells.

When an electrode is now placed in the tissue, it is possible

to change the outer membrane potential by applying a particu-

lar voltage to this electrode. In this way it is possible to

Figure 2: Electrical stimulation anno

1820 according to Richard Reece. A

manually controlled non implantable

device. State of the art neural stimulators

are surprisingly similar to this ancient

medical device.

Figure 3: Existing stimulators have

limited implantability. The stimulator

can only be implanted in the chest,

while subcutaneous wires lead to

the electrodes in the brain (Image

courtesy of Medronic inc.)


change the membrane voltage and therefore action potentials

can be artificially generated or blocked. In this way the func-

tionality of the brain can be directly influenced.

Therefore neural stimulation is from an electrical point of view

nothing more than elevating the tissue potential (the outer

membrane potential) up to a particular threshold. Electrical

modeling of the electrode-tissue interface shows a capacitive

nature. This means that elevating the tissue potential above

a particular threshold corresponds to injecting a particular

amount of charge in the tissue. This observation has been a

critical starting point in the project.

Design of the stimulatorThe fact that charge is the fundamental electrical quantity for

stimulation can be used to design an effective stimulator. How-

ever another important design aspect is safety. When applied

in the correct way, stimulation can lead to beneficial results in

the brain. However, stimulation can also lead to damage to the

tissue when certain requirements of the stimulation waveform

are not met.

One of the basic safety constraints is that no net charge can be

injected into the tissue. Charge at the electrode tissue interface

will lead to electrolysis, which is harmful to the tissue. This

means that after a stimulation pulse some mechanism must

make sure that the injected charge is removed from the tissue

again. One fast way to do this is by applying a second, negative

pulse with the same charge contents.

Taking these aspects in mind, one of the first choices for the

design of a stimulator is the electrical quantity which is used

to inject the electrical energy into the tissue. Most of the exist-

ing stimulators use constant value current sources to stimulate

the tissue, as illustrated in Figure 5a. In this way the amount

of charge injected can be quite easily controlled: by enabling a

constant current for a particular amount of time, the charge is

defined as Q=It. There are however a few important drawbacks

related to current sources:

High power consumption

For charge cancellation, the value of the current source must be

equal during the stimulation phase as well as the charge cancel-

lation phase. To create accurately matched current sources, a

lot of power is required. This will increase the size of the bat-

tery. Current stimulators have limited implantability, because

of the size constraints which are determined by the battery. In-

creasing the power efficiency is therefore very important.

Waveform flexibility

One major drawback of the existing stimulators is the limited

adjustability of the waveform. To be able to control the charge

easily, usually only square shaped pulses can be injected. Neu-

ral tissue shows an amazing adaptability to stimulation. This

means that due to the fixed stimulation pattern the tissue will

gradually habituate to the stimulation pattern, which means

the symptoms of the disease return.

It is expected that habituation can be reduced when it is pos-

sible to generate varying stimulation waveforms. Furthermore a

wide waveform choice can result in more effective stimulation.

Examples include sinusoidal or triangular shapes, asymmetric

stimulation and a wide variety of burst stimulation. Using cur-

rent sources it is hard to realize this: the charge is not controlled

as easy anymore compared to the constant current approach.

Based on the two observations above and because current is

not a fundamental quantity, it was decided to look into alterna-

tive electrical quantities to steer the tissue. It was shown that a

voltage source (see Figure 5b) yields a much better approach: it

is much more power efficient and it is easy to make a variable

voltage source for waveform flexibility.

Figure 4: Structure of a typical neuron and a detail of a cell membrane (Image courtesy of Mariana Ruiz and Quasar Jarosz, modified under the Creative

Commons BY-SA license.)


The drawback of a voltage source approach is that the charge is

not easily controlled anymore, since the current is determined

by the tissue impedance, which is very time variant. Therefore

it was decided to include a current feedback loop to keep track

of the charge injected. In this way it is possible to use any wave-

form, while still ensuring charge cancellation.

A new type of system architecture was proposed using indirect

current feedback. This also implied the use of an additional

voltage feedback loop to control the tissue voltage. This dou-

ble feedback architecture has been implemented in Amis 0.35μ

high voltage technology (stimulation voltages used are up to

20V). This principle is depicted in Figure 6.

The implementation details of the system are beyond the scope

of this article, but probably the most challenging part of the

design was the current feedback loop in which an integrator

needed to determine the charge injected based on the stimula-

tion current. This integrator was required to handle a dynamic

range of several decades of magnitude.

ResultsSimulation results on circuit level show the feasability of the

system. An example of a stimulation waveform generated by

the circuit (1kHz, 2V amplitude and 7V offset) was injected

into the tissue (modeled as a parallel combination of a resistor

of 10k and a capacitor of 75nF). The charge threshold was set

to 171nC. The transient simulation result of the tissue volt-

age is depicted in Figure 7. As can be seen, the tissue is first

charged to about -2.3V during the first (negative) voltage pulse.

Subsequently a positive pulse is injected to remove the charge

at the tissue. As can be seen the resulting tissue voltage is very

close to zero, indicating the charge metering technique is work-

ing properly.

One of the design goals was to have a very low power consump-

tion to increase the implantability of the device. Active power

consumption is very dependent on the waveform used. There-

fore it is hard to quantify the active power consumption or ef-

ficiency of the design.

The quiescent power consumption is however as low as 15μW.

Most of this power is burnt in the voltage feedback network

to bias the gain stage here. Furthermore the switches require

some bias to generate a floating voltage source controlling the

switches. The quiescent power consumption is to the best of

our knowledge among the lowest values for quiescent power

consumption reported until now.

An important safety performance parameter is charge mis-

match. In the waveform from Figure 7 the remaining charge

was 1.5nC, corresponding to about 1%. About 50% of this

mismatch is due to discharge of the tissue in the inter-pulse

delay because of the finite off resistance of the switches in the

switch array. This mismatch can therefore easily be removed

when the inter-pulse delay is chosen to be shorter. Further an-

other 40% of the charge imbalance is due to inaccuracies in the

implementation of the integrator. When these inaccuracies

Figure 5: Illustration of two possible fundamental stimulation architectures

Figure 6: The principle of indirect current feedback with direct voltage

feedback, which is used as the fundamental system architecture.

a. Current steered b. Voltage steered

0 1 2 3 4 5 6 7 8

x 10−3

−8

−6

−4

−2

0

2

4

6

8

Time (s)

Tis

sue

volta

ge (

V)

Figure 7: Tissue voltage during excitation with a sinusoidal waveform.

The final tissue voltage is close to 0V, illustrating the feasibility of the

system.


are improved, the charge mismatch will become 0.1%. Any

remaining charge can be discharged from the tissue by short

circuiting the tissue electrodes using the switch array if needed.

Another safety parameter is the ability to handle the large spread

in stimulation and tissue parameters. The system is working

for any combination in tissue parameters ranging from 1k <

R < 100k and 10nF < C < 100μF. Furthermore the system is

also working over all process corners and process mismatches,

preserving charge cancellation.

Because of the chosen architecture there are endless possibili-

ties for waveform adjustments. In principle any waveform can

be used: the charge metering mechanism will keep track of the

charge injected in the tissue. It is therefore possible to use tonic

stimulation, burst stimulation, asymmetric stimulation, sub-

threshold prepulses, excitatory and inhibitory stimulation, etc.

To illustrate this two waveforms for both tonic and burst stimu-

lation are depicted in Figure 8. This figure illustrates the charge

cancellation mechanism is working for a wide variety of shapes,

since the final voltage is very close to zero.

ConclusionsIt has been shown that electrical stimulation of the brain opens

up a huge field of treatments for a wide variety of diseases. Be-

cause of the highly selective properties of neural stimulation it

can offer more effective treatments in many cases compared to

the use of drugs.

The physical principles underlying electrical stimulation of

neurons have been investigated in detail. It was shown that

from a electrical point of view the stimulation of neural tis-

sue is equivalent to raising the extracellular potential up to a

particular threshold value. Because of the capacative nature of

the electrode tissue interface, this is equivalent to injecting a

particular amount of charge into the tissue.

Taking this principle in mind, a fundamental new system ar-

chitecture was designed and implemented on the circuit level.

Simulation results confirm the feasibility of the system. Fur-

thermore the system has a very versatile character (endless

waveform possibilities), very low power consumption, while

safety is still assured.

This design opens the way to more efficient neural stimulation

treatment methods. Still, there is much room for improvement.

System blocks like the external communication, power man-

agement and an automated feedback loop (stimulation based

on recording neural activity) still need to be designed. There-

fore this project will continue in order to design the remaining

system blocks to finally come up with a completely new and

revolutionary neural stimulator.

The project is carried out in cooperation with many univer-

sity hospitals, especially the BRAI2N clinic in the University

Hospital of Antwerp (UZA). The multidisciplinary approach of

this project is something I have very much enjoyed during the

course of the project.

If you have questions related to this article or you are interested

in the details of the electronic implementation, you are very wel-

come to contact us. Within our group we are also always looking for

motivated students who are willing to contribute to this challeng-

ing project or other projects in the biomedical field. The contact

details for me and my supervisor Wouter Serdijn are as follows:

0 2 4 6 8

x 10−3

−8

−6

−4

−2

0

2

4

6

8

time (s)

Tis

sue

volta

ge (

V)

0 2 4 6 8

x 10−3

−8

−6

−4

−2

0

2

4

6

8

time (s)

Tis

sue

volta

ge (

V)

0 2 4 6 8

x 10−3

−8

−6

−4

−2

0

2

4

6

8

time (s)

Tis

sue

volta

ge (

V)

0 2 4 6 8

x 10−3

−8

−6

−4

−2

0

2

4

6

8

time (s)

Tis

sue

volta

ge (

V)

Figure 8: Illustration of the endless waveform shape possibilities. The tissue voltage is showed for two different tonic and burst stimulation waveforms,

while charge cancellation is preserved.

Biomedical electronics group, Elca Research Laboratory,

Mekelweg 4, 2628CD Delft

Marijn van Dongen dr. ir. Wouter Serdijn

Room HB 18.030 Room HB 18.310

[email protected] [email protected]


HIER INVOEGEN:PAGINA21TNO.PDF

22 Maxwell 13.3 Aprli 2010

AvionicsThe main contributor to innovation in aviation

The need for a specialization of Electrical En-

gineers in the area of Avionics was already rec-

ognized in 1976 by prof. van Oosterom from

the Faculty of Aerospace Engineering at Delft

University of Technology (at that time still TH

Delft). To address the identifi ed need, in 1979

the Faculty of Electrical Engineering started a

special program which aimed to educate inter-

ested students with a background in Electrical

Engineering in the area of Avionics. At present,

it is an interfaculty specialization profi le. Al-

though having been restructured several times

in the past 30 years, the core philosophy of the

program remains the same:

• Use a set of coherent courses from the Fac-

ulty of Aerospace Engineering and the Faculty

of Electrical Engineering to provide the students

with the background needed to successfully

perform an M.Sc. research project in the area of

Avionics.

• Focus the Avionics research on a number

of internationally recognized challenges and

pursue them through international cooperation.

• Maintain a state-of-the-art research infra-

structure to provide an inspiring learning and

research environment.

The frequent reception of best-student paper

awards at the largest international Avionics con-

ference (organized jointly by IEEE and AIAA)

and the contribution of many former EWI Avi-

onics students in highly visible international

research programs (such as the NASA Aviation

Safety Program) prove that this approach is very

successful. To provide EWI students that are

fascinated by aviation a better idea of how they

can obtain the required background for a future

career in the fi eld of Avionics, this article starts

with a brief overview of today’s challenges. Us-

ing examples from previous and current inter-

national research projects, it is illustrated how

M.Sc. and Ph.D. students and researchers from

EWI have contributed to defi ning the future

state-of-the-art in Avionics.

Figure 1 (background): Cockpit of EWI simulator.


Avionics refers to Electronic systems used in Aviation, and the word itself is a blend of Aviation and

Electronics. Avionics are not only essential for today’s commercial and military aircraft to fl y, but also

enable their integration into the overall traffi c management system. For safety critical applications such

as navigation, aviation imposes requirements and constraints on the electronics system which are far

more stringent than for example in the consumer electronics domain. This has an impact on the design

of the Avionics.

Author: Dr.ir. Erik Theunissen

Innovation in aviationWhen comparing a Boeing 747 that was built in

1969 with a Boeing 747 built in 2010, the biggest

leap in capabilities can be attributed to Avionics.

Engines have become far more effi cient through

the use of Fully Autonomous Digital Engine

Control (FADEC). Safety has increased through

the introduction of the Enhanced Ground Prox-

imity Warning System (EGPWS) and the Traffi c

alert and Collision Avoidance System (TCAS).

Through better integration and automation,

the number of crew members that is required

to operate the aircraft has been reduced to two.

The instrument Landing System (ILS) provides

the capability to land under zero visibility con-

ditions, and the Flight Management System

(FMS) allows fuel optimized path to be fl own.

Indeed, in the past 40 years, a large part of the

innovation in the aviation domain was the re-

sult of developments in the area of Avionics.

The reason for this leap is that for Avionics the

enablers lie in the electronics domain and hence

many capabilities advance with the speed of

Moore’s law. Also today, the challenge for Avi-

onics is to benefi t from this advantage when ad-

dressing the issues aviation is confronted with.

The following four issues are internationally re-

garded as top priorities:

1. Reduction in the environmental burden

caused by aviation

2. Further increase in safety, both in the air

and on the airport

3. Further increase in airport availability (inde-

pendent of the actual weather)

4. Integration of unmanned aircraft into con-

trolled airspace

Environment: There is still ample potential

of Avionics to reduce the burden of Aviation

on the environment. The theme of the IEEE/

AIAA 2010 Digital Avionics Systems Confer-

ence (DASC) is ‘Greening Aviation’. Whereas

today’s instrument landing system only


provides guidance for straight-in approaches, future Avion-

ics systems, enabled by more accurate and reliable sensors,

will support precision guidance along curved paths. This

provides the opportunity to circumvent noise sensitive ar-

eas that lie below the current approach paths. Through op-

timized navigation in the vertical dimension, the current

transitions between level and descending path segments

during an approach can be minimized or even eliminated,

allowing a significant reduction in the required engine

thrust and thus reducing emissions. To safely fly these more

complex approaches, advanced cockpit displays are required

to provide the pilot with the information needed to assess

whether the aircraft stays free of any hazards.

Safety: During the past thirty years, the major improve-

ments in the safety of commercial aviation were achieved

through the extrapolation of sensor-based information. To

reduce midair collisions, TCAS interrogates the transpond-

ers on board of other aircraft to determine whether there is

a collision hazard. Likewise, GPWS uses data from the radar

altimeter to determine whether the aircraft inadvertently is

getting close to the terrain. In the past ten years, the devel-

opments in the area of compact data storage have allowed

GPWS to be augmented with a warning system that relies

on the use of a worldwide terrain database and GPS-based

position information. These databases can also serve to pro-

vide the pilot with a synthetic view of the environment, in-

dependent of visibility conditions. Before actual operational

credit can be taken for this capability, a concept is needed

that timely detects hazardous discrepancies between the da-

tabase and the real world.

Availability: Whereas large airports such as

Schiphol are equipped with guidance systems that

allow properly equipped aircraft to land under

zero visibility conditions, many smaller airports

do not have such equipment. Reasons comprise

cost of the required infrastructure but also loca-

tion. In a mountainous environment, today’s ILS

cannot be deployed because of undesired signal

reflections. A navigation system that meets or

exceeds the accuracy, continuity and integrity re-

quirements of today’s (ground-based) ILS without

requiring significant infrastructure on the ground

is one of the top priorities for Avionics research.

Unmanned aircraft: Recent guidance from the

U.S. Federal Aviation Administration (FAA) sug-

gests that self separation needs to be a component

of an Unmanned Aircraft System (UAS) Sense

and Avoid solution in order for UAS to behave similarly to

manned aircraft. Conceptually, UAS self separation is the

protective (or conflict avoidance) method that precludes a

threat aircraft from ever triggering a time-critical collision

avoidance maneuver. To realize such a self-separation ca-

pability requires an Avionics system comprising sensors to

detect the collision hazards, algorithms to filter out observa-

tion noise and compute solutions for those threats that are

identified as real ones, and user interface concepts to allow

an operator to monitor the situation.

Avionics research @EWIWithin the EWI Avionics research program, specific chal-

lenges related to the aforementioned issues are being ad-

dressed. To benefit from similarities between the differ-

ent challenges, the research is structured along common

themes such as integrity, path optimization and human

machine interfaces. The expertise at EWI covers hardware,

software, algorithms, user-interfaces and system interfaces,

allowing the multidisciplinary challenges that are typical

for Avionics to be properly addressed. The EWI Avionics re-

search has an excellent reputation on an international level.

In 1998 the Faculty of Electrical Engineering (EE) was in-

vited by industry to join them in an effort to compete for re-

search in the context of the NASA Aviation Safety Program.

As part of a team lead by Avionics manufacturer Rockwell

Collins, synthetic vision system prototypes were developed,

integrated and first flight tested in 2000. Based on the re-

sults, Avionics researchers from EWI further refined these

prototypes and in 2001 the resulting system was success-

Figure 2: Cockpit of NASA 757 with EWI SVS.

Maxwell 13.3 Aprli 2010 25

fully evaluated in the NASA Boeing 757 during

the Eagle-Vail flight tests (figure 2). In August

and September 2001 more than 100 continu-

ous descending curved approaches were flown

in a terrain challenged environment.

One of the Avionics students that became in-

volved in the research in 1999 during his M.Sc.

project stayed on as a part-time researcher and

was one of the three engineers that Rockwell

Collins allocated to support this NASA flight-

test program. For the contribution to the over-

all NASA Aviation Safety program the Turning

Goals Into Reality Award was received.

The system test flown in 2001 relied on the

use of a digital terrain database to provide the pilot with

information about the terrain hazards. The Achilles-heel

of any database-oriented system is that errors in the data-

base can cause terrain hazards present in the flight path of

the aircraft not to be depicted. To enable timely detection

of hazardous discrepancies between the real environment

and the synthetic environment, the prototype system was

extended with the capability to integrate a real-time sen-

sor images. In 2004, four EWI Avionics researchers partici-

pated in the NASA flighttests during which this system was

evaluated (figure 3).

As indicated earlier, part of the focus is on unmanned sys-

tems. Several Avionics students performed their research in

this area on topics such as automatic landing systems, air-

space integration and the use of networks to achieve control

from geographically separated locations. Prototypes of UAV

mission management stations developed in a joint project

between EWI and the Royal Netherlands Naval College are

used by the Royal Netherlands Air Force to explore new

concepts of operation using mission level simulations.

The amount of rewards that has been received indicates

that the quality of both the M.Sc. projects and the overall

research is internationally recognized. In 2005, M.Sc. stu-

dent de Vries received the IEEE/AIAA Best Student Paper

Award at the DASC for his Avionics research project. The

following year, M.Sc. student ‘t Hart received this award for

his M.Sc. project that focused on UAV control. In the past

five years, the Avionics research was awarded with a total

of fourteen international awards, two of which (in 2007 and

2008) were ‘Best of Conference’.

Avionics education @EWIThe EWI Avionics program prepares interested students

with the background required to become an Avionics En-

gineer. This involves both courses such as ET4138 which

focus on the Avionics systems and courses at Aerospace

Engineering dealing with aircraft performance (AE4-220ET)

and flight dynamics (AE3-302)

The Avionics program is supported through an excellent

research infrastructure. Room 20.320 on the 20th floor

houses a research UAV operator station with which new

concepts for mission management can be evaluated. Room

20.070 houses a research flight deck, equipped with a pro-

grammable Electronic Flight Instrument System, a Flight

Management System, simulation of all required sensor

systems, and a projection system to simulate the view out

of the cockpit (figure 1). This flightdeck is used both for

research projects and in the avionics education program

(ET4244).

Avionics is a fascinating area and quite frequently students

that became involved with a particular topic during their

M.Sc. project continued to work in this area. Some during

a subsequent PhD research project, some as a researcher

at EWI or another University such as Ohio, and others at

institutes such as NLR, organisations such as LVNL and

companies such as ADSE and Rockwell Collins.

If you are a student at EWI and fascinated by aviation, you

should certainly consider the opportunity to become an Avi-

onics engineer. EWI provides an excellent Avionics educa-

tion program that prepares you for a future where you can

successfully compete with the best of the best.

Figure 3: Interior of NASA GV.


Innovatie in TrammetjeslandEen van de meest onderstreepte features van de nieuwe TU campus is de tramlijn die door de TU-wijk

zal gaan rijden. Prof. Lou van der Sluis vertelt ons in een interview een paar leuke weetjes over de verni-

euwingen op het gebied van bovenleidingloze trams en wat dit te betekenen heeft voor tramlijn 19, die

door het Mekelpark zal lopen.

Auteurs: Ben Allen en Benjamin Gardiner

De aanleg van tramlijn 19 is al aardig op

weg. Merkbaar zelfs, voor iedereen die 18

maart op de TU wijk aanwezig was. Tij-

dens graafwerkzaamheden is een 10kV

kabel geraakt, die dezelfde dag nog ver-

vangen moest worden. Als consequentie

hiervan kwam de TU-wijk een avond lang

zonder elektriciteit te zitten, waardoor de

bezigheden neergelegd moesten worden

en alle gebouwen ontruimd werden. Ook

gaan er geluiden over de campus dat de

faculteit Technische Natuurwetenschap-

pen niet erg blij is met de tram vanwege

storende invloeden

die de bovenleiding

zou veroorzaken.

Op zoek naar de

waarheid gingen

bovenstaande auteurs op bezoek bij pro-

fessor Lou van der Sluis, om te vragen

welke van die geruchten waar zijn en wat

we kunnen verwachten bij de implemen-

tatie van tramlijn 19. In rood de vragen

danwel opmerkingen van bovenstaande

auteurs, in zwart de reactie van professor

van der Sluis.

Wij hadden gehoord dat u iets meer wist

over de draadloze tram die door het Me-

kelpark komt en daar wilden wij graag

iets meer over weten.

Er komt een tram door het Mekelpark,

lijn 19, maar dat heeft een vervelend ne-

veneffect. De bovenleiding van de tram,

daar loopt natuurlijk een stroom door, die

een magneetveld gaat produceren. Dat

magneetveld zou in een aantal gebou-

wen, en met name TNW (Technische Na-

tuurwetenschappen, red.), zeer gevoelige

metingen kunnen

beïnvloeden. Dit

is natuurlijk erg

vervelend, dus wat

we gedaan hebben

is in een klein comité een compensatie-

systeem bedenken. Dat compensatiesy-

steem is bedacht door Prof.dr.ir. P. Kruit

en dat is later naar de markt gewerkt door

een projectgroep waar ik de voorzitter van

was.

“ER KOMT EEN TRAM DOOR HET MEKELPARK, LIJN 19, MAAR DAT HEEFT EEN VERVELEND NEVENEFFECT.”

Je kunt de bovenleiding zo uitvoeren dat

je geen last meer hebt van de magneet-

velden op een afstand van 100 meter.

In de trammetjeswereld is er echter een

ontwikkeling gaande dat trammetjes op

batterijen en accus beginnen te rijden,

en tegenwoordig gaat dat ook met een

supercapaciteit. Dat is het College van

Bestuur ter ore gekomen, en die hebben

toen gevraagd: “Kunnen we niet van die

bovenleiding af?” Dat scheelt kosten, en

de bovenleiding verpest het uitzicht niet.

Dus wordt er ook gekeken naar de moge-

lijkheid van zo’n accutram. Maar je hebt

ook een maatschappij die de tram moet

laten rijden – de HTM – en die heeft een

plan voor het aanschaffen van nieuw ma-

terieel. De oplossing hier moet ook in

dat plan passen. Dus of er over het Me-

kelpark een trammetje zal rijden op ac-

cus of supercapaciteit, dat weet ik niet. Je

moet sowieso wel kijken naar innovatie

in Trammetjesland.

Met het oog op de route van lijn 19 door

Ypenburg, is het nou het idee dat de tram

alleen in het Mekelpark zonder bovenlei-

ding zou rijden, of over het hele traject?

Nou, de actieradius van zo een tram is erg

beperkt, dat is eerder honderden meters

dan kilometers, dus in het uiterste geval

ben je na een of twee kilometers wel klaar.

In Nice hebben ze zo een tram rijden - als

je namelijk een beschermd stadsgezicht

hebt is dat een leuk alternatief. Het voor-

WAT IS EEN SUPERCONDENSATOR?

Supercondensatoren hebben een capaciteit die

vele malen groter is dan die van een conventi-

onele elektrolytische condensator. De techniek

die toegepast wordt stelt men in staat om veel

hogere energiedichtheden te halen. Op moment

van schrijven is de hoogste energiedichtheid die

geproduceerd wordt 30 W·h/kg.

Figuur 1. Een 2.5V 350F supercondensator.


deel van zo een tram op accus is dat als de

tram remt, kan je die energie opnemen in

de accus en weer optrekken door gebruik

te maken van deze energie. Per saldo, van

de energiekosten uitgerekend, zou je die

tram wel eens terug kunnen verdienen.

Wij zijn eigenlijk wel nieuwsgierig naar

het compensatiesysteem. Hoe hebben

jullie dat voor elkaar gekregen?

Je hebt wel eens gehoord van een magne-

tische dipool, denk ik. Een magneet is ui-

teraard een magnetische dipool. Maar als

je een door een draadje een stroom stuurt,

in een kringetje, dan krijg je een magne-

tisch veld en dan heb je ook een magne-

tische dipool. En op een afstandje weet

je niet of het een statisch veld is van een

draadje of van een magneet. Die magneti-

sche dipool komt dus doordat dat draadje

een oppervlak heeft. Dus als je je voorstelt

dat de bovenleiding de stroom aanvoert,

gelijkstroom, gaat die door de pantograaf,

door de motor, en via de rails weer terug

naar de voeding. Nu zie je dat daar een

enorme lus in zit - dat is de dipool. En de

vraag is dus “hoe krijg ik die dipool weg?”

Wat we bedacht hebben is om de dipool

weg te halen door de draadjes heel dicht

bij elkaar te leggen.

Je knipt de bovenleiding in stukjes. De

palen van die bovenleiding staan op 40

meter van elkaar en de bovenleiding knip

je door bij elke paal. Als je in gedachten

houdt dat de retourstroom via de rails

gaat en als je nou de voedende kabel langs

de rails legt en je trekt hem bij de paal

op en verbindt hem met de bovenleiding,

dan heb je dus maar een heel klein lusje

gecreeerd en die tram gaat van lusje naar

lusje naar lusje. Op die manier heb je die

dipool enorm verkleind.

Ik vraag me af hoe die supercondensato-

ren danwel accus van energie voorzien

worden, ik neem aan dat ze die uit de bo-

venleiding halen?

Ja ja, dat is zo. Hetzelfde idee wordt ge-

bruikt voor de Rijngouwelijn, dus Gouda

- Leiden - Katwijk, daar willen ze ook

bepaalde stukken geen bovenleiding heb-

ben, daar ben ik ook een beetje bij betrok-

ken. Je zou dus kunnen denken dat je bij

elke halte, zodra de tram stilstaat, hem

even oplaadt, dan heb je helemaal geen

bovenleiding meer nodig. In Nice is het

zo, dat hij in stukjes zonder bovenleiding

rijdt en op sommige stukken wel. Dat is

een mooie oplossing voor het opladen.

Bij de Rijngouwelijn is het toch zo dat Lei-

den aardig dwarsligt? Wordt het een tra-

ject met alleen bovenleiding of maakt de

accutram nog een kans?

Er is nog niets besloten. De provincie

heeft nou een studie bij mij uitbesteed

om te kijken of dat haalbaar is of niet.

De kogel is dus nog niet door de kerk.

Figuur 2. Een tram in Amsterdam

ACCU’S

Een andere mogelijkheid dan de super-

condensator is de welbekende Li-ion

accu. Dezelfde technologie die in je lap-

top zit kan, indien groot genoeg uitge-

voerd, trams en auto’s laten rijden. Be-

kend voorbeeld: De Toyota Prius.


The following description of an American breakfast is taken from www.busi-

nessdictonary.com: American breakfast generally includes most or all of the

following: two eggs (fried or poached), sliced bacon or sausages, sliced bread

or toast with jam/jelly/butter, pancakes with syrup, cornfl akes or other ce-

real, coffee/tea, orange/grapefruit juice.

Right. I think that having such a breakfast every morning is probably not

the healthiest thing to do. I have to admit, however, that now and then I do

prepare American pancakes for breakfast. Once, during a conference visit in

the US, I had pancakes and I was immediately hooked. They tasted really

good and since then I occasionally turn the kitchen into a pancake factory.

Ingredients (for 3 to 4 persons) Flour (300 grams)

Buttermilk (0.5 liter)

Four teaspoons of baking powder

Four eggs

Two or three tablespoons of granulated

sugar

Two tablespoons of melted butter

One teaspoon of salt

Cooking with…Rob Remis

American Pancakes

American pancakes (also known as hotcakes, griddlecakes, or fl apjacks) are easy

and fun to make, especially for a leisurely Sunday breakfast or brunch. Before

messing up your kitchen, you might want to set the breakfast table fi rst, and make

sure that everything looks nice. Now the real “cooking” can start. First, combine

all the dry ingredients (salt, sugar, fl our, and baking powder). Then whisk the eggs

and the milk and blend in the melted butter. Finally, mix everything until there

are no lumps left. Cook your pancakes on a hot griddle (a fl at and rimless pan).

You can check the temperature by pouring a little bit of water on the surface of the

griddle. When the water sizzles, the griddle is ready for action. For each pancake,

pour ¼-cup of batter onto the hot surface of the griddle and turn your pancake over

as soon as bubbles start to appear. This is it, basically. There is really nothing to it.

To keep your pancakes warm, place them in a mildly hot oven.

Serve your pancakes with butter and syrup and add your own favorite toppings. I

like to serve my pancakes with bacon and fresh fruit (bananas or strawberries, for

example), but other tasty toppings such as chocolate chips, powdered sugar, jam,

or raisins also go very well with pancakes.

Enjoy!


HIER INVOEGEN:PAGINA29MASTERVOLT.PDF


TTEthernet

A Powerful Network Solution for All Purposes

Author: Dr. Markus Plankensteiner, Head of Marketing TTTech Computertechnik AG

From Ethernet to TTEthernetOver the last years there has been discussion about how to

adapt Ethernet for new application domains. Its focus has

been on the use of Ethernet for real-time tasks in industrial

environments. More than 20 different approaches are now

struggling for recognition in industrial automation alone.

Today’s Ethernet systems have limits when it comes to

combining them with classical Ethernet networks, de-

vices and services. The scalability of these systems is also

limited and the network solution is tailored for a specifi c

application area. TTEthernet combines the proven deter-

minism, fault-tolerance and real-time properties of the

time-triggered technology

with the fl exibility, dynam-

ics and legacy of “best effort”

of Ethernet and is therefore

suited for all types of appli-

cations.

Considering networking

technologies in general, one

can distinguish between

closed, statically confi gured

embedded networks and open, dynamic networks allowing

free-form communication. Whereas statically confi gured

communication networks enable reliable data transmis-

sion in real time, free-form communication networks per-

form only on a best-effort basis, i.e., there is no guarantee

if and when data messages are transmitted. As statically

confi gured systems usually need to comply with strict safe-

ty are based on dedicated standards, the number of com-

munication nodes is known and not very fl exible. Open

standards, like the TCP/IP/Ethernet stack that drives the

Internet, form the basis of free-form communication and

the number of nodes in systems is arbitrary. TTEthernet

brings together the high fl exibility of free-form systems and

the reliability and speed of statically confi gured systems

(see Figure 1).

TTEthernet Design ObjectivesTTEthernet enables the seamless communication of all

applications by way of Ethernet. Conventional PCs, web

and offi ce devices, multimedia systems, real-time systems

and safety-critical systems are to use the same network. A

single network that is completely compatible with the IEEE

Ethernet 802.3 standards is suited for data transmission

among different applications with various requirements. A

single network solution could thus be used for all appli-

cations in airplanes, ranging from the entertainment pro-

gram, to board supply, electronic navigation and guidance

system, and internet access in passenger seats. Critical ar-

eas are accordingly made fail-safe or fail-operational. Fault

tolerance mechanisms avoid the fault propagation in the

system and prevent potential hackers from unauthorized

access to resources.

TTEthernet is scalable. Networks that connect uncriti-

cal applications shall be able to transmit real-time data in

distributed controls and shall be suited for safety-critical

applications in the future. Existing applications need not

be changed when the network is extended in terms of func-

tionality. Time-critical messages always take precedence

over less important messages in TTEthernet. This does

not affect conventional applications. The temporal behav-

ior of the time-critical messages is predictable and can be

characterized depending on the required quality.

Fig. 1: TTEthernet combines closed-

world and open-world systems on the

basis of IEEE 802.3 Ethernet standards.


TTEthernet is used for safety-critical fail-operational ap-

plications. This means that the system remains fully func-

tional even if a failure occurs No matter if a node, a switch

or a network branch is faulty, the network continues safe

communication. This fact accounts for the essential dif-

ference between TTEthernet and other Safe Ethernet sys-

tems. The latter systems, which are sufficient for industrial

applications detect faults in the network and switch the

system to a safe state, e.g. stopping the engine. In order

to secure the availability of the system even if a failure oc-

curs, TTEthernet provides a variety of network services

such as a clock synchronization service, a startup service

and clique detection and recovery services. The behavior

of TTEthernet is precisely predictable and thus formally

verifiable.

TTEthernet System PropertiesTTEthernet has time-triggered services that enable time

triggered communication over Ethernet. These time-trig-

gered services establish and maintain a global time, which

is realized by the close synchronization of local clocks of

the devices. The global time forms the basis for system

properties such as temporal partitioning, precise diagnosis,

efficient resource utilization, or composability.

Temporal Partitioning: The global time can be used as

a powerful isolation mechanism when devices become

faulty; we say that the global time operates as a “temporal

firewall”. In case of failure it is not possible for a faulty ap-

plication to untimely access the network. Depending on

the location of the failure, either the communication con-

troller itself or the switch will block faulty transmission

attempts. Failures of the switch can be masked by powerful

end-to-end arguments such as CRCs or by high-integrity

designs.

Efficient Resource Utilization: The global time contrib-

utes to efficient resource utilization in several ways. Time-

triggered communication allows minimizing the memory

buffers in network devices as the time-triggered commu-

nication schedule is free of conflicts. Hence, switches do

not have to be prepared for bursts of messages that have to

be delivered over the same physical link. A minimal time-

triggered switch design could even multiplex media access

logic such as reception or transmission logic. A second

way of effective resource utilization is buffer memory in

the nodes, which can be minimized as the sensor values

can be acquired according to the global time, immediately

before sending the message. Finally, a third way of effective

resource utilization is power management in which energy

can be seen, and saved, analogously to memory.

Precise Diagnosis: A global time stamping service simpli-

fies the process of reconstruction of a chain of distributed

events. On the other hand, the synchronous capturing of

sensor values allows building snapshots of the state of the

overall systems.

Composability: The global time allows the specification of

devices not only in the value domain, but also in the tem-

poral domain. This means that already during the design

process of devices, the access pattern to the communica-

tion network can be defined. The devices can then be de-

veloped in parallel activities. Upon integration of the indi-

vidual devices, it is guaranteed that prior services are stable

and that the individual devices

operate as a coordinated whole.

Dataflow Options in TTEthernetTTEthernet specifies services

that enable time-triggered com-

munication on top of Ethernet.

The time-triggered services can

be viewed parallel to the usual

OSI layers: a communication controller that implements

these services is able to synchronize with other communi-

cation controllers and switches in the system. It can then

send messages at points in time derived from this system-

wide synchronization. These messages are then called

time-triggered messages.

As TTEthernet supports communication among applica-

tions with various real-time and safety requirements over

a network, three different traffic types are provided: time-

triggered (TT) traffic, rate-constrained (RC) traffic, and

best-effort (BE) traffic. If required, the corresponding traffic

type of a message can be identified based on a message’s

Ethernet Destination address. The relation of the TTEth-

ernet traffic types to existing standards is depicted in Figure

2.

Messages from higher layer protocols, like IP or UDP, can

be “made” time-triggered without modifications of the

messages’ contents itself. The TTEthernet protocol over-

head is transmitted in dedicated messages termed protocol

control frames, which are used to establish system-wide

synchronization. In short, TTEthernet is only concerned

Fig. 2: Relation of TTEthernet to

existing communication standards


with “when” a data message is sent, not with specific con-

tents within in a message.

TT messages are used for time-triggered applications. All

TT messages are sent over the network at predefined times

and take precedence over all other traffic types. TT mes-

sages are optimally suited for communication in distrib-

uted real-time systems. TT messages are typically used for

brake-by-wire and steer-by-wire systems that close rapid

control loops over the network. TT messages allow design-

ing and testing strictly deterministic distributed systems,

where the behavior of all system components can be speci-

fied, analyzed and tested with sub-micro second precision.

RC messages are used for applications with less stringent

determinism and real-time requirements than strictly

time-triggered applications. RC messages guarantee that

bandwidth is predefined for each application, and delays

and temporal deviations have defined limits. RC messages

are used for safety-critical automotive and aerospace appli-

cations that depend on highly reliable communication and

have moderate temporal quality requirements. Typically,

RC messages are also used for multimedia systems.

In contrast to TT messages, RC messages are not sent with

respect to a system-wide synchronized time base. Hence,

different communication controllers may send RC mes-

sages at the same point in time to the same receiver. As a

consequence, the RC messages may queue up in the net-

work switches, leading to increased transmission jitter. As

the transmission rate of the RC messages is bound a priori

and controlled in the network switches, an upper bound on

the transmission jitter can be calculated off-line and mes-

sage loss is prevented.

BE messages follow a method that is well-known in clas-

sical Ethernet networks. There is no guarantee whether

and when these messages can be transmitted, what delays

occur and if BE messages arrive at the recipient. BE mes-

sages use the remaining bandwidth of the network and

have less priority than TT and RC messages. Typical user

of BE messages are web services. All legacy Ethernet traffic

(e.g. internet protocols) without any QoS requirement can

be mapped to this service class. TTEthernet implements

strong partitioning between non-critical BE traffic and all

other service classes (see Figure 3).

TTEthernet as Transparent Synchronization Pro-tocolTTEthernet is a transparent synchronization protocol, i.e.,

it is able to co-exist with other traffic, potentially legacy

traffic, on the same physical communication network. For

reasons of fault tolerance a multitude of devices can be con-

figured to generate synchronization messages. The devices

generating the synchronization messages may be distribut-

ed with a high number of intermediate devices in between

each other.

Fig. 4: A test setup for TTEthernet

Fig. 3: TTEthernet includes TT, RC and BE messages.


TTEthernet defi nes basic building blocks that allow the

transparent integration of the time-triggered services on

top of message-based communication infrastructures such

as standard Ethernet. For this, TTEthernet defi nes a novel

application of the transparent clock mechanism that ena-

bles the concept of the permanence point in time, which

allows re-establishing the send order of messages in a re-

ceiver:

Application of transparent clock mechanism: all devices

in the distributed computer network that impose a

dynamic delay on the transmission, reception, or relay of

a synchronization message add this dynamic delay into a

dedicated fi eld in the synchronization messages used for

the synchronization protocol.

Novel precise calculation of the permanence point in

time: the application of transparent clock mechanism

allows a precise re-establishment of the temporal order

of synchronization messages. In a fi rst step the worst

case delay is calculated off-line. In a second step, each

synchronization message is delayed for ”worst case delay

minus dynamic delay” upon reception of the synchroniza-

tion message, where the dynamic delay is the delay added

to the synchronization message, as the synchronization

message fl ows through the communication channel. This

point after the reception point in time will be called the

permanence point in time.

For fault-tolerant algorithms in general, and fault-tolerant

synchronization algorithms in particular, the message send

order is of highest importance. The re-establishment of

the send order of synchronization messages is required for

any fault-masking synchronization protocol that ensures

synchronization of local clocks in a distributed computer

network.

Safety and Fault ToleranceA high level of safety is provided by the time-triggered

method of TTEthernet, which detects failures and irreg-

ularities in the network and certain systems. Additional

measures need to be taken to achieve maximum safety,

availability and fault tolerance.

Contact: TTTech Computertechnik AG

Schoenbrunner Strasse 7

A-1040 Vienna, Austria

Tel.: +43 1 585 34 34-0

Fax: +43 1 585 34 34-90

E-mail: [email protected]

Web: www.tttech.com

TTEthernet networks can be set up with multiple redun-

dant end systems, switches and segments. Thus the system

will remain in operation even if faults occur. Redundant

network paths are always used in fault-tolerant TTEther-

net systems so that the failure of a single system or mes-

sages can be tolerated without affecting the application. If

multiple redundancy is implemented, multiple faults can

be tolerated. It is important that the entire system remains

in operation without interrupts under the same temporal

conditions as defi ned before.

TTEhernet allows the integration of guardians in switches

and end systems. Guardians check if the communication

on the network works in compliance with the predefi ned

parameters. If faulty systems block network segments, the

guardian disconnects the network segment or port. Multi-

ple redundant guardians can be implemented to meet the

highest safety requirements).

ConclusionTTEthernet enables time-triggered communication over

Ethernet networks in all application areas. The network

provides all necessary mechanisms for applications as di-

verse as classical web services and time-critical and safety-

critical control system in airplanes. Existing networks can

be extended step by step using TTEthernet-capable switch-

es and end systems without the need to change existing

applications and end systems. Reducing network solutions

to established and recognized Ethernet standards opens up

saving potentials that secure major advantages in competi-

tive markets.

Fig. 5: A network card as used by TTTech for testing.


Joost may know itHoe werkt een plasmabol?

Author: Benjamin Gardiner

De plasmabol is een voorwerp dat in het kader valt van fascine-

rende objecten, net als de lavalamp. Kenmerkend aan deze ob-

jecten is dat je er uren naar kan staren met de vraag hoe ze nou

werken. Vandaag zal ik jullie vertellen hoe één van deze objecten

werkt, namelijk de plasmabol.

Je hebt vast gezien hoe in een plasmabol alle bliksemflitsen naar

de buitenkant van de bol gaan en hoe je dit effect kan verstoren

door je hand op het glas te leggen. Als je dit doet gaan de blik-

semflitsen naar je hand toe, maar waarom?

Een plasmabol is opgebouwd uit drie verschillende onderdelen.

De eerste is de elektrode in het midden van de plasmabol en

dient voor het opbouwen van het potentiaalverschil. Het tweede

onderdeel is het medium waar de bliksemflitsen zich doorheen

bewegen, dit is meestal een edelgas maar een gas als stikstof kan

ook. De reden waarom lucht niet geschikt is, komt doordat lucht

geen duidelijke vonken maakt en het potentiaalverschil een stuk

hoger moet zijn dan bij edelgassen. Het derde deel van de plas-

mabol is de glazen bol om de plasmabol. Deze dient simpelweg

voor het vasthouden van het gas.

Wat is een plasma? Plasma wordt ook wel gezien als de vierde ag-

gregatietoestand. Plasma ontstaat door atomen op te warmen tot

heel hoge temperaturen. Daardoor beginnen de atomen met gro-

te snelheden te bewegen zodat, telkens als ze botsen, de elektro-

nen weggerukt worden uit de atomen. Zodoende bestaat plasma

uit positief geladen ionen en de elektronen die van de atomen

zijn losgekomen. Dit kan ook gerealiseerd worden door een hoog

potentiaalverschil aan te brengen waardoor de elektronen van de

kernen worden los getrokken.

Wat is nou de reden dat die bliksemflitsen naar je hand toe gaan

als je deze op het glas legt. Dit komt doordat de ionen die zijn

ontstaan bij het ioniseren van het gas nieuwe elektronen zoeken.

Door jouw hand op de glazenbol te leggen creëer je een aardpunt

waar nieuwe elektronen vandaan kunnen komen. Zo ontstaat er

door je lichaam naar aarde een stroom, deze voel je niet omdat

hij zeer klein is. De ionen zoeken nieuwe elektronen en worden

daardoor aangetrokken naar het aardpunt wat in dit geval jouw

hand is, dit zie je vervolgens als bliksemflitsen die in de richting

van jouw hand bewegen.

Plasmabollen


HIER INVOEGEN:PAGINA35NAVIGON+PINEWOOD.PDF


The Nuon Solar Team and their famous car the Nuna had a great tradition of winning the World Solar

Challenge in Australia. Four times in a row the car was faster than all the other solar cars. This year,

however, it was different. Some headlines claimed we lost first place, others said we won second. Be-

cause of all the hard work our team put in the car, I would agree with the second one. We had a great

fight with the Michigan solar car and managed to stay in second position. This year’s winning car, from

Japan, was way ahead of us from the first day on. So, what went wrong with the legendary Nuna? Why

was the fifth victory out of our reach?

Before the raceThree weeks before the race in Darwin, Australia, the car

was getting into shape and testing went well. We could fi-

nally start to change our team from a group of engineers to

a well-oiled racing team. At the point where none of us ex-

pected it, it all went terribly wrong. The rear tire blew and

Nuna became unstable. The driver could no longer control

the three wheeled vehicle because the most import one of the

three was no longer there.

Nuna went off-road with a speed of approximately 100km/h

which resulted in a spectacular crash. Large parts of the so-

lar panels were damaged, most of the suspension was gone

and, of course, a lot of bodywork was ripped away. Luckily

most of the structural parts were still intact and probably the

most imported part, the driver, could get out without a single

scratch. After an analysis of what had happened we pulled

the team back together and started the rebuild. With a lot of

support from our sponsors we managed to get the car run-

ning again within two weeks. We could finally start testing

again but we did lose a valuable 2 weeks of race preparations.

Four days of troubleDuring the race the electronics of our precious lady Nuna

performed a bit disappointing. A lot of systems that we used

for monitoring the car stopped working, or only worked a

part of the time. The most important issue was a failing

MPPT (Maximum Power Point Tracker). Even when we re-

placed the tracker with a fresh one it would stop working

within an hour. And, most surprisingly, the old one worked

fine in the test environment. It took us four days to find the

problem. What was the cause of this stupid problem I will

discuss later. First I will go into the details of the tracker.

IV CurveThe first question you might have is why we would need an

MPPT between the solar panel and the battery of the car.

Well, as the name suggest, it is to get a maximum amount

of power from the sun. This all depends on the voltage curve

of solar cells.

When a photon hits a solar cell an electron is kicked out of

the semiconductor material. The intensity of the light deter-

mines the flow of electrons. If a constant amount of photons

per second hit the material, a constant amount of electrons

will be kicked out of the cell. This behavior can best be mod-

eled whit a current source.

To get the maximum amount of power out of a current source

we should keep the voltage as high as possible. However if we

do this with a solar cell we will suffer from recombination

Figure 1: The Nuna5 after crashing.

Nuna5:What went wrong?Author: Rico van Dongen


and the cell starts dissipating most of the energy on its own.

With some cells you can even see this effect when the cell is

left in the sun without a load. Suddenly small red lights ap-

pear on these cells. Also hotspots can appear that sometimes

become so hot that they burn trough the cell (Figures 2&3).

In figure 4 an IV curve (blue line) of an arbitrary silicon solar

panel is given. The red line in this figure shows the multi-

plication of voltage and current, the PV curve. It is clearly

shown that the maximum amount of power can be drawn

from this panel by adjusting the output voltage to the point

where it starts going down. This lower voltage prevents the

electrons from recombining with their holes and makes sure

that all the power goes to the battery.

MPPTThe maximum power point (MPP) of a solar cell is constantly

shifting due to changing weather conditions. When the sun

intensity is low the MPP shifts to a lower voltage. Of course

a battery can only be charged when the voltage is higher than

its own voltage so there need to be some sort of conversion.

That is why the tracker is basically an adjustable boost con-

verter. A special tracking algorithm tests certain point on the

IV curve and makes sure the converters input voltage is near

the MPP.T These testing points are the yellow dots in figure

4. When the intensity of the sun changes the MPPT has to be

adjusted to the new intensity. Compared to the tracking algo-

rithm these changes are slow so by simply trying different points

the converter goes back to the MPP. Some trackers are also able

to detect the slope of the PV curve and thereby knows if it has to

increase or decrease its input voltage.

Failing connectionsSo, now we know what the tracker should do. But why did it

stop working during the race? Probably the cause was in the

mounting of the board. One support had some minor fab-

rication errors that caused some tension on the PCB of the

tracker. After a while the board would heat up and expand a

bit. This expansion caused some extra tension that resulted

in a broken contact. This stupid problem caused us about

one quarter of the total solar input power. This means that

we came in second with only three quarters of the energy.

Quite an achievement if you ask me.

Better luck next timeOf course we all learned a lot during the design and build

phase of the Nuna project, but we probably learned the most

during the 5 days of intense racing. I am sure that the next

team will put some special care in the supports of all the

PCB’s and improve the design even more. Then, the Nuna6

will be able to win the race again and maybe even break

the world record. This record is still in the hands of Nuna3

which could drive up to 103kph average thanks to the more

flexible regulations.

To make sure the new team knows all the details about

Nuna we now started a special course. Under the cover of

the course ‘sustainable mobility and transport’ (AE4-T39),

we now go through the complete design. If you would like a

taste of the Nuna race spirit and know more about the design

of Nuna5 feel free to follow this course. But of course, if you

really want to know how amazing it feels to design, build and

race a solar car you will have to join the Nuna6 team.

Figure 2: Thermal image - normal. Figure 3: Thermal image - hotspot.

Figure 4: IV-curve.


Everybody who has seen a James Bond

movie, or anything involving spying of

any sort, has heard of the concept of a

bug. A small electronic device is placed

in a person of interest’s room, and the

agents in the other room can listen in

on what’s going on. Evidence is gathered,

and the story can move on.

Of course, in reality things are a little dif-

ferent. The microscopic devices used in

Hollywood are slightly more advanced

than what we can achieve on our bread-

boards. Unless you have a very steady

hand or access to an smd soldering oven

you’re not going to be able to replicate the

miniature devices seen in the movies.

Legal concernsThere are a few less frivolous concerns

when it comes to radio circuits. Radio

frequency transmissions are strictly regu-

lated and simply transmitting on AM/FM

bands is illegal - something that has shut

down many decent pirate radio station

in the past. The reason for this is sim-

ple: you need a license to use a certain

frequency - and these licenses are sold at

auction. Because commercial radio sta-

tions are also interested in acquiring a

license to transmit, these become incre-

dibly expensive. As such, transmitting on

AM band is illegal in the Netherlands.

Luckily, there is a provision in the law for

low-power FM devices, for instance to lis-

ten to your iPod in the car without having

to fit a new stereo system.

Please note that the power allowed for

these devices is severely limited. The cir-

cuit we have featured has a range of about

20-30 metres, but more powerful devices

step over the low-power boundaries and

as such are not permitted.

Listening inBefore we can even start to think about

transmissions, we need something to

transmit. In our case, we’re looking to

transmit audio. In figure 1 we have a

simple one-transistor amplifier that takes

Circuit BodgingFM bug transmitter

Many people have their interest in electronics start with radio. As much as radio is taken for granted by

most people, the idea of sending information through the through the air at the speed of light remains

enticing to anyone who thinks about it for longer than a few minutes. As such, we submit to you this

simple yet effective FM transmitter.

Author: Ben Allen

its input from a condensor microphone.

A condensor microphone (figure 2) is a

special type of microphone in which the

diapraghm (the moving part of the mi-

crophone) acts as one of the plates of a

capacitor. As the diaphragm moves, the

capcitance changes.

Figure 1. The condenser microphone

and surrounding circuitry.

Figure 2. A number of electret condenser

microphones.


Part list:

R1: 22kR2: 1M R3: 10kR4: 47kR5: 470

C1: 223pFC2: 100nFC3: 102pFC4: 5.6pFC5: 27pFC6: 6-45pF trimmer

L1: 1μH

ANT1: simple antenna

T1, T2: BC547

Using a microphoneThe circuitry in figure 1 is fairly self-

explanatory. One thing to take into ac-

count is that the condenser mic needs a

voltage to be applied across the device for

it to operate. Unlike dynamic micropho-

nes, condensers don’t create an output by

themselves. We are, in essence, measu-

ring and amplifying the change in the de-

vice’s behaviour as opposed to measuring

an output from the device itself.

Turning it into radioThe interesting stuff happens in figure 4.

First of all, note that the input does not

have a DC filtering capacitor. This is be-

cause the microphone amplifier circuit

already features this capcitor, C2. If you

intend to use the circuit to broadcast so-

mething other than the output from the

microphone you should add the 100nF

capacitor in series with the input.

C6 and L1 provide an oscillator, the fre-

quency of which can be adjusted with C6.

When tuning the circuit, tune your radio Figure 4. The RF modulator.

to 90MHz and attempt to recieve a signal

whilst adjusting C6.

Because the capcitance of T2 is in the

same order of magnitude as C6, the idea

is that as the transistor amplifies the in-

put, this capcitance influences the oscil-

lator, causing the frequency to change -

Frequency Modulation.

This is presented, once again through a

DC filtering cap, to the antenna, which

broadcasts the signal.

Power supplyThe power requirement of the circuit is

very simple, as shown in figure 3. A 3-5V

supply is enough, so a series connection

of 3 AAA cells can power the circuit easi-

ly. The large 470μF capacitor C7 provides

smoothing in the case of external power

supplies.

Final NotesMaking an FM transmitter out of discrete

parts is notoriously unreliable. A simpler,

but less interesting way is to use ICs to

provide modulation, as all they require is

an input signal and an antenna, and in

some cases a crystal for the oscillator. If

your goal is reliability as opposed to expe-

rimentation, an IC such as the MC2833

or the MAX2606 might be more to your

liking.

Figure 3. Power supply


Via via werd ik gevraagd of ik op een elektrische

scooter namens de gemeente Delft wilde deelne-

men aan de Road to Copenhagen. Als vierdejaars

student Electrical Engineering en Bestuurder van

de Electrotechnische Vereeniging is dit een vraag

waarop maar één antwoord mogelijk is: ja! Niet

alleen is het een geweldige uitdaging, ook is het

een buitenkansje om de Elektrotechniek weer

eens voor het voetlicht te halen.

Toen ik mij meer ging informeren over de actie,

las ik dat een groep van wel honderd jongeren op

scooters naar Kopenhagen zou gaan rijden, om

daar tijdens de klimaatconferentie afgelopen de-

cember een manifest aan de wereldleiders aan te

bieden.

Aanvankelijk was ik daarom bang dat ik met een

stel hippies naar Kopenhagen zou gaan. De groep

was echter erg divers. Zo waren er studenten be-

drijfs- en bestuurskunde, internationale betrek-

king en duurzame ontwikkelingen. Ik was een van

de weinige technische studenten. Ondanks deze

ogenschijnlijke cultuurbarrière zijn we al snel een

hechte gezellige groep geworden. Het hoofddoel

van de tocht was, naast het promoten van duurzaam vervoer, het aan-

bieden van een manifest aan de wereldleiders die op dat moment aan de

klimaattop deelnamen.

De scooter waar ik op reed werd gesponsord door Delft en was onder

handen genomen door het Delftse bedrijf Epyon. Daarom kon deze in

een half uurtje volgeladen worden, in tegenstelling tot de andere negen-

tig scooters. Voor de gemeente Delft was deze tocht een goede manier

om hun betrokkenheid bij duurzame ontwikkelingen te tonen. Per dag

werd er vier uur gereden. Geheel conform de tijd van het jaar was het

rijden erg koud. Gewapend met thermo-ondergoed, een

fl eecetrui en een dikke winterjas reed ik in vijf dagen de

eerste etappe, van Den Bosch naar Osnabrück.

Wanneer we niet op de scooter zaten, werden we ver-

maakt met lezingen, workshops of excursies. Deze dien-

den als inspiratie voor het manifest dat we aan het einde

van de tocht in Kopenhagen aan de wereldleiders hebben

aangeboden. In dit manifest staan twaalf tips om een

duurzamere samenleving te verwezenlijken. Zo kwam

mijn groepje met het idee om het voor consumenten

duidelijker te maken dat zuinigere producten op de lange

duur goedkoper zijn. In de supermarkt staat verplicht op

Samen met honderd andere studenten reed de Com-

missaris Onderwijs van de ETV, Frank Teunisse, de

‘Road to Copenhagen’ om tijdens de klimaattop

aandacht te vragen voor duurzaam vervoer.

Per elektrische scooter naar KopenhagenAuteur: Frank Teunisse


Naast al deze serieuze activitei-

ten werden we goed verzorgt;

iedere dag, soms zelfs al in de

lunch, stond er een heerlijke

warme maaltijd op ons te wach-

ten, ter compensatie voor de

koude ontberingen van die dag.

Alsof dat niet genoeg was, werd

de dag afgesloten met een goed

feest. Echter, na een korte nacht

in een jeugdherberg moesten we

voor acht uur al weer klaar staan

voor de volgende dag.

Het meest indrukwekkend vond

ik zonder twijfel het meerijden

in een Tesla Roadster. De Tesla

is een elektrische sportauto, ver-

noemt naar uitvinder en Elec-

trotechnisch ingenieur Nikola

Tesla (1856 – 1943). Met recht heeft deze wagen de titel ‘sportauto’, aan-

gezien de ‘0 tot 100km per uur’ al in 3.7 seconde gehaald kan worden. En

dat deed hij dan ook. Het voelde als in een achtbaan, ik werd helemaal in

mijn stoel gedrukt. Het piepen van de banden was daarbij het enige wat ik

hoorde, want de motor produceert slechts een miniem gezoem.

Al met al ben ik zelf niet veel “groener” geworden van deze ervaring. Ik

ben me wel veel meer van bewust van het klimaatprobleem en ik geloof nu

wel dat dat ook echt een probleem is. Momenteel wachten consumenten

en het bedrijfsleven op elkaar om te investeren in bijvoorbeeld elektrisch

vervoer. Aan zet is, wat mij betreft, dan ook de overheid. Zij kan zowel de

burgers als het bedrijfsleven stimuleren te investeren in duurzame pro-

ducten. Deze reis heeft mij in ieder geval kunnen overtuigen dat elektrisch

vervoer een volwaardig alternatief voor vervoer op brandstof is. Nu is het

wachten op de grote massa.

alle producten hoeveel calorieën een portie bevat.

Wanneer er op een lamp verplicht staat aangege-

ven hoeveel deze per jaar kost, zijn mensen veel

eerder geneigd een duurdere, maar in gebruik

goedkopere, LED-lamp te kopen.

De meest interessante lezing was die van Mi-

chael Braungart, Hoogleraar Cradle-to-Cradle

aan de Erasmus Universiteit Rotterdam. Zijn

idee is dat energie bespáren alleen tot gevolg

heeft dat men minder slecht is voor het milieu.

Waar men vanuit zou moeten gaan, is dat je iets

positiefs aan het milieu toevoegt, in plaats van zo

min mogelijk negatiefs. Zo heeft Braungart mee-

gewerkt aan een duurzame wolkenkrabber in de

woestijn, die meer energie en water opbrengt dan

de inwoners zelf gebruiken.


Conceptual ‘CTRUS’ football gets loaded with sensors, don’t need no pumpWe’ve heard of soccer

balls that play a tune

when kicked, sure,

and we’re pumped

to see the World

Cup in 3D, but it’s

not often that someone

comes up with a serious

technological makeover for

the sport that’s nearly as old as

life itself. CTRUS, however, is just

that - a theoretical revolution in soccer

that begins with the all-important ball. To start with, a reinforced elastic

structure means that CTRUS doesn’t require any air. (So long, pump.)

Next, GPS and RFID chips keep track of the ball’s position at all times,

and tell it to light up in different colors when it scores a goal or is ac-

complice to a nefarious violation. (Farewell, referee.) Last but not least,

the sphere itself will report back with accelerometers that measure the

ball’s kick force and travel speed, and a camera that could (with magical

software stabilization, of course) actually fi lm action from the ball’s own

POV. Sadly, the ball is just a concept from an undercover

marketing agency, but since we’re dreaming, we

urge its creators to add a second camera. Just

imagine just how immersive it would be to

have your face booted in at 130km/h in glo-

rious 3D. Or, just peek the concept videos

after the break.

Source: www.gizmodo.com

Tiny Generators Charge Up From Random Vibrations In the AirWhat’s an easier green power source to acquire than

sun or wind? Random ambient vibrations, that’s what.

And that’s exactly how some new generators juice up.

The devices, created by researchers at the University

of Michigan, aren’t going to be powering your cars any-

time soon, but they’ll be able to gather enough energy

to power watches, pacemaker or wireless sensors.

The vibrations they pick up are from things like traf-

fi c on bridges, machinery operating in factories or you

swinging your arms around.

The researchers have built three prototypes and a

fourth is forthcoming. In two of the generators, the

energy conversion is performed through electromag-

netic induction, in which a coil is subjected to a vary-

ing magnetic fi eld. This is a process similar to how

large-scale generators in big power plants operate.

The latest and smallest device, which

measures one cubic centimeter, uses

a piezoelectric material, which

is a type of material that

produces charge when it is

stressed. This version has

applications in infrastruc-

ture health monitoring.

The generators could one

day power bridge sensors

that would warn inspec-

tors of cracks or corrosion

before human eyes could

discern problems.


Auteur: Technolution B.V.

Gedreven door ontwikkelingen in de 3D-

gamingmarkt zijn zeer snelle grafische

processors ontwikkeld. Bij de eerste gra-

fische toepassingen rekende de CPU van

de pc pixel voor pixel het weer te geven

beeld uit. Daarna werd pixel voor pixel

het beeld naar de videokaart gestuurd.

Vervolgens gaf de videokaart slechts de

pixels weer. Dit is een zeer rekeninten-

sieve klus, zeker als dit bijvoorbeeld in

een 3D-game bij 30 frames per seconde

moet gebeuren met een resolutie van

1920 x 1200. In de jaren negentig kwa-

men steeds krachtigere videokaarten

voor de consument op de markt en kreeg

de videokaart zijn eigen processor, de

GPU. In plaats van pixel voor pixel de

videokaart aan te sturen worden objec-

ten en instellingen aangeleverd, zodat

deze aparte processor zelfstandig werk

kan verrichten naast de CPU.

StandaardisatieIn de 3D-gaming, een consumenten-

markt, worden zeer grote volumes van

deze processors verkocht. Omdat de

producenten van de GPU’s en de games

verschillende bedrijven zijn, ontstond de

noodzaak tot standaardisatie van de in-

terfaces (API’s). De belangrijkste 3Din-

terfacestandaarden zijn DirectX/Di-

rect3D en OpenGL. In de praktijk komt

het erop neer dat de GPU-producenten

strikt de gespecificeerde functionaliteit

van deze 3D-interfaces (API’s) volgen.

ATI (nu AMD) en NVIDIA zijn bekende

producenten van GPU’s. De kern van

3D-spellen is dat een virtuele 3D-wereld

op het scherm wordt afgebeeld vanuit

het perspectief van een (virtuele) speler,

met een snelheid van bijvoorbeeld 30

frames per seconde. Dit wordt gereali-

seerd door een hele reeks bewerkingen

in een vaste volgorde uit te voeren. Dit

proces heet een rendering pipeline.

GeschiedenisIn de jaren negentig kwamen steeds

krachtigere videokaarten voor de consu-

ment op de markt. En een steeds groter

deel van de rendering pipeline werd in

hardware uitgevoerd. De bewerkings-

stappen in de rendering pipeline zijn de

zogenaamde shaders. Bijvoorbeeld een

vertex shader voegt bepaalde 3D-effec-

ten toe aan objecten, een geometries-

hader genereert nieuwe objecten vanuit

al gedefinieerde objecten en een pixels-

hader berekent de kleur van een pixel.

Een belangrijk nadeel was dat met het

vastleggen van de specifieke shaders in

hardware ook de rekenkracht per shader

vast lag. Dit terwijl verschillende spellen

verschillende eisen stelden aan de verde-

ling van de rekenkracht tussen de ver-

schillende shaders. Relatief recent is er

als onderdeel van de DirectX-standaard

een Unified Shader Model gespecifi-

ceerd. Het betreft een processormodel

dat uitgerust is met een instructieset

die geschikt is voor de functionaliteit

van alle verschillende typen shaders.

Het voordeel van dit concept is dat per

stap van de rendering pipeline de volle-

dige rekenkracht aangewend kan worden

en programmeerbaar is. Met dit nieuwe

type grafische processor is ook de eerste

praktische mogelijkheid ontstaan om de

GPU voor ander rekenwerk in te zetten.

Rekenkracht moeilijk te temmenDe hedendaagse GPU beschikt over een

enorme rekenkracht. Hij kan tot wel 30

keer meer floating pointberekeningen

verwerken dan een reguliere CPU (zie

figuur). Dat klinkt geweldig: zoveel meer

rekenkracht in een processor voor glo-

baal dezelfde prijs. Dat wil iedereen wel.

Maar als iets te mooi klinkt om waar te

zijn, dan is het dat vaak ook. Aan een ‘al-

ternatief ’ gebruik van een GPU, anders

dan als grafische kaart in een pc, kleven

de nodige mitsen en maren. Het reken-

kundige probleem moet goed passen op

de architectuur van een GPU, evenals

de floating pointprecisie en het is

GPU: brute kracht inzetbaar voor meer dan alleen beelden?

De GPU (Graphics Processing Unit) in een moderne pc is een waar

rekenmonster. Bij het produceren van een vloeiende stroom beel-

den voert de GPU meer berekeningen perseconde uit dan de pro-

cessor (CPU). Maar in de praktijk blijkt het niet eenvoudig GPU’s

intezetten voor andere toepassingen.


praktisch niet mogelijk om een GPU te

combineren met een andere hardwarear-

chitectuur dan die van een pc.

Dieper in de techniek van de GPUIs het verhaal dan klaar met de conclu-

sie dat de GPU elk jaar betere beelden

maakt, maar een plaatjesmachine is en

blijft? Zo zwart/wit liggen de zaken niet.

In bepaalde gevallen en onder strikte

voorwaarden zou een GPU als alterna-

tief kunnen dienen voor ander zwaar

rekenwerk dan alleen grafisch werk.

Daarvoor moeten we iets dieper in de

techniek duiken. Een GPU is een paral-

lelle processor: hij voert zeer veel paral-

lelle bewerkingen uit. Dat is bijvoorbeeld

te zien aan de brede geheugenbussen, tot

wel 256 bits. Ter vergelijking: de CPU

is nog niet zo lang geleden van 32 naar

64 bits gegaan. Een GPU werkt dus

met veel meer data tegelijk. Maar het

ontwerp is bedoeld voor eenrichtings-

verkeer: er komt een brok data binnen

met elementaire beeldinformatie, voor

elke pixel berekent hij het een en ander,

vervolgens stuurt hij dat er aan de an-

dere kant uit richting het beeldscherm.

Een GPU is slecht in keuzes maken,

zoals in het doorlopen van typische “if

..., then ..., else ...”- softwareconstruc-

ties. Daar wordt hij traag van. Een GPU

is juist gebouwd om voor alle parallelle

paden hetzelfde te doen. Dat heet sin-

gle instruction, multiple data (SIMD).

Er is een instructiedecoder en een hele

groep executie-units. Zodra er een keuze

komt, kan die maar voor een executie-

unit gelden en kunnen de anderen niets

effectiefs doen. Een gewone processor is

veel beter in het oplossen van if-then-

else-problemen. Die kan slim door een

reeks van voorwaarden en afhankelijk-

heden heen slalommen en zich veel re-

kenwerk besparen, als een skiër die in

de afdaling continu kiest en stuurt om

de snelste weg te vinden. Een GPU is

als een roeiboot met bijvoorbeeld acht

roeiers die tegelijkertijd samen een doel

proberen te bereiken. Als elke roeier een

ander parcours zou moeten varen, dan

kan dat alleen maar door acht parcour-

sen achterelkaar te varen met telkens

één roeier aan het werk. Een GPU is

dus goed in het parallel verwerken van

rekenkundige bewerkingen volgens vaste

formules.

Berekeningen aansturen met APIAls een GPU gebruikt gaat worden,

moet dat gebeuren met speciale instruc-

ties, die bij elk merk GPU kunnen ver-

schillen. Hierbij zijn de standaard API’s

niet bruikbaar. Het is dus hard nodig om

toegang tot de GPU’s te standaardiseren,

zodat de functies die moeten worden uit-

gevoerd op een redelijk abstract niveau

kunnen worden aangeboden. Op dit mo-

ment zijn de belangrijkste twee: CUDA

van NVIDIA en de merkonafhankelijke

variant OpenCL (Open Computing Lan-

guage). OpenCL is initieel gedefinieerd

door Apple Inc., maar is door hen via

de Kronos Groep tot een open standaard

gemaakt. Door deze API’s te gebruiken

kunnen de ingewikkelde details van een

GPU worden beheerst en kan de pro-

grammeur zich richten op het onder-

havige probleem. Ook zullen door stan-

daardisatieprogramma’s (bv. Matlab) er

bibliotheken ter beschikking komen met

GPU-ondersteuning voor veel voorko-

mende problemen, zodat niet iedereen

opnieuw het wiel hoeft uit te vinden.

Rekenkracht GPU anders aan-wendenDoor de genoemde API’s is, zoals eerder

aangegeven, het mogelijk om goed pas-

sende rekenkundige problemen, zonder

uitvoer naar een beeldscherm, met suc-

ces sneller op een GPU uit te voeren

dan op een CPU. Gedacht moet worden

aan o.a. matrixberekeningen en Fourier-

transformaties, zoals die bijvoorbeeld

voorkomen in ruimtelijke problemen als

3Dsimulaties van stromingen of elektro-

magnetische velden. Dit zijn verschijn-

selen die zich laten analyseren door de

wereld in kleine vakjes of kubusjes te

verdelen om per vakje een natuurkun-

dige vergelijking op te lossen (ook wel de

eindige elementenmethode genoemd).

Het oplossen van deze vergelijkingen

vergt heel veel ‘simpele’ rekenstappen

op een grote dataset, maar ook andere

grootschalige berekeningen (vooral floa-

ting point) en beeldgeneratie voor de

professionele en wetenschappelijke ge-

bieden. Voor dit soort toepassingen heeft

NVIDIA een professionele GPU ontwik-

keld onder de naam Tesla. Een onderzoe-

Figuur 1: Droomscenario: GPU versus CPU

Optimale inzet van een GPU voor beeldbewerking kan bovenstaande curve opleveren (met fors meer

MIPS voor de GPU dan bij de CPU). Buiten die specifieke grafische toepassing is een GPU beperkt.

Het draaien van niet-grafische toepassingen op een GPU zou een ander plaatje laten zien: de perfor-

mance stort in tot onder de CPU-curve.


ker heeft zo voor een relatief bescheiden

bedrag een desktop die qua rekenkracht

kan wedijveren met een supercomputer.

GPU in embedded systemen?Voor professionele technische toepassin-

gen is een GPU alleen maar bruikbaar

in zijn natuurlijke habitat: op een gra-

fische kaart, ingebouwd in een pc, met

standaard software. Mochten GPUchips

al los verkrijgbaar zijn, dan nog zijn ze

moeilijk in embedded systemen in te

passen. Het probleem moet passen bij de

architectuur van de chip, de chip moet

passen in het systeem en het business-

model moet kloppen. Zo heeft de GPU

voor zijn inzetbaarheid bij grafische

toepassingen een korte levensloop en is

daardoor slecht verkrijgbaar op de lange

termijn. De professionele embedded we-

reld is vrijwel altijd beter uit met een

FPGA. Die zijn wel lang genoeg lever-

baar. De keus in FPGA’s is enorm: voor

elk denkbaar probleem is wel een speci-

fieke FPGA te vinden. Deze zijn ook nog

eens uiterst flexibel. De ontwikkelaar

kan namelijk zelf de balans kiezen tus-

sen parallel en serieel, tussen data load

en rekenkracht. Soms zijn er niet zoveel

afzonderlijke berekeningen nodig, maar

moet het wel op 10Gb datastromen ge-

beuren, zoals in een hoge resolutiecame-

ra. Die genereert een bulk data die eerst

wordt bewerkt voordat een pc er iets mee

kan. Misschien zou dat met een GPU

kunnen, maar voor bewerkingen in het

embedded domein kiest Technolution

er altijd voor om de datastroom met een

FPGA te bewerken. Juist vanwege voor-

genoemde zaken.

Toekomst GPUEen van de grootste beperkingen van

vandaag in het parallel rekenen is de

doorvoersnelheid van het geheugen. Lar-

rabee is de codenaam van een ontwik-

keling bij Intel, die een hybride van een

X86 CPU en een GPU in een smeedt tot

een GPGPU (General Purpose GPU). In

dit geval wordt gebruik gemaakt van vele

volwaardige CPU-kernen met SIMD-

support en een conventionele cache.

Door in de toekomst een CPU- en een

Larabeechip te integreren komen beide

typen processoren op een plak silicium

te zitten en kunnen de verbindingen erg

kort en dus snel zijn. Dit geeft veel flexi-

biliteit en performanceverbetering voor

een breder scala rekenintensieve toepas-

singen. De performanceclaims van Intel

worden door de bestaande GPU-specia-

listen met de nodige scepsis benaderd.

Als deze combinatiechip slaagt, zou hij

het einde van de losse grafische kaart

kunnen inluiden en dus geheel nieuwe

toepassingen voor de GPU in beeldbren-

gen.

Dit artikel is overgenomen uit Objective

12, het magazine over innovatie en tech-

nologie van Technolution op management-

niveau.

Hier invoegen: pagina45Technolution_half.pdf


Buitengrenzen van TU DelftNa mijn bijna 46-jarige carriere (van student tot hoogleraar-directeur onderzoeksinsti-

tuut IRCTR) op TUDelft wil ik u deelgenoot maken van mijn persoonlijke ervaringen

met TUDelft buitengrenzen.

Wat merk je van TUDelft buitengrenzen als je bezig bent met het afstuderen. Eigenlijk

niet zoveel. Je volgt nog enkele colleges, je hebt contacten met je medestudenten, men-

tor en afstudeerhoogleraar. Dan ga je een baan zoeken. Al snel kom je erachter, dat er

TUDelft buitengrenzen zijn. Bij bedrijven waar je solliciteert zitten veelal oud TUDelft

studenten (alumni) op belangrijke posities. Alumni bepalen zo de beeldvorming van de

TUDelft buitengrens voor de pas afgestudeerde.

Contacten met onderzoeksorganisaties lopen veelal via daar werkende onderzoekers

met een ir. titel. Dan blijkt, dat alumni gaarne bereid zijn jou te woord te staan. Tevens

wordt snel duidelijk dat meerdere alumni een behoorlijke carriere maken en dat zij met

trots de relatie duiden tussen hun positie en de TUDelft opleiding.

ColumnAuteur: Prof. Dr. Leo Ligthart

Mijn passie is internationaal onderzoek. Al in het begin van de 70-tiger jaren had ik interesse voor in-

ternationaal contractonderzoek; laten we zeggen 3e geldstroom onderzoek; alhoewel, termen als 1ste,

2de en 3de geldstroom bestonden toen nog niet. Mijn bevoegdheid tijdens projectonderhandelingen

bestond eruit dat indien er problemen waren, ik mijn ‘professor-baas’ moest bellen. Kortom, er waren

weinig beperkingen.

Als hoogleraar heb ik mijn buitengrenzen verder kunnen verleggen wetende dat kennis over een

bepaald universitair vakgebied geen grenzen kent. Dankzij samenwerking met geselecteerde sterke

internationale onderzoeksteams zijn mogelijke oplossingen van grote maatschappelijke problemen

haalbaar. Deze problemen zijn meestal multi-disciplinair en vereisen een leerstoel (ja zelfs een TU-

Delft) grens-overschrijdende aanpak en de opzet van zogenoemde internationale doorbraakprojecten.

Om mijn multi-disciplinair onderzoek maximaal te faciliteren is het onderzoeksinstituut IRCTR (In-

ternational Research Centre for Telecommunications and Radar) opgericht. IRCTR kreeg erkenning

van het Ministerie van OC&W en werd vereerd met een bezoek van de toenmalige minister Ritzen.

Inmiddels zijn er internationale IRCTR branches en vele samenwerkingsverbanden met bedrijven en

universiteiten. Hierdoor kunnen studenten en promovendi, niet alleen uit Delft maar ook van partner

universiteiten, participeren in internationale programma’s.

Wat is mijn buitengrens: niet de universiteit te Delft of de campus van Delft, maar de partnerinstitu-

ten. Als ik nu een werkbezoek breng binnen of buiten Europa zijn er altijd oud-afstudeerders, die in

eerdere projecten hebben meegedaan en die het op prijs stellen om blijvende contacten met TUDelft

en IRCTR in het bijzonder te onderhouden. Mijn TUDelft buitengrenzen liggen bij al mijn oud-

studenten, -promovendi en -onderzoekers, die als ambassadeurs van TUDelft op weg zijn naar de

top van wetenschappelijke instituten danwel bedrijven of deze positie reeds bereikt hebben. Zij allen

waren eens student en hebben bijgedragen aan de over de grens erkende internationale status van het

TUDelft radar- en telecommunicatie onderzoek.


HIER INVOEGEN:PAGINA47ASML.PDF

48 Maxwell 13.2 January 2010

HIER INVOEGEN:PAGINA48FARNELL.PDF

axwell - TU Delft

Documents

Transcript of axwell - TU Delft